*snip*

As many developers have said, ports do not do the Wii U justice. The Wii U is powerful, but games have to be made for it.

Working with AI and game design are two different things entirely, conventional AI doesn't need to take into account resource management anywhere near as much and does not need to be situationally aware in most applications, but since you asked, here we go.

Ingame enemy versus active enemy.
Games have always strived to have a bunch of enemies, it makes for a more exciting game,  however having a large number of active AI running at once is not viable in almost all situations, so comprimises are made, two stage or even three stage AI to stagger the processing requirements based on likelyhood of contact with the player.

Generally this is done in one of two formats

Idle > Follow > Active
or
Idle > Triggered alert > Active

But for games intending to have large mob based fights we end up with active being replaced with queued active.

In countless games you'll get mobbed by enemies, but only a few will actually engage with the player at once, the few engaging are the active pawns that have the most advanced AI routine of the set, requiring the use of the enemies skillset, animation flow control, attack routine, defend routine and in some cases heal routine / flee when in danger routine, the non active enemies at this point, the ones crowding around you but not attacking, are either in follow state, or triggered alert, both of which basically move to follow the user and stay within proximity, in the case of mob brawlers, those within a set distance from the player can be in queued active state where they will switch to active either because the active pawns drop back to queued, are defeated, or flee.

To make this clearer i'll break down the states.

Idle
pawn is in lowest state mode, often not actually running AI, just simple scripting to handle motion animation and have the pawn move around in a set area, each pawn has a simple proportional range of triggered detection to move it up into the next state, in some games this is a range dictated by central axis to the pawn over a set fov and distance, in less complex games simply a set radius around the enemy itself

Follow / Triggered
in this secondary state, which is skipped entirely by certain enemy types (such as non-aggressive monsters only attacking when attacked) the main focus of this state is to move the enemy over to the player for melee, or to prepare the enemy to face a particular direct (fps) or switch to a "seek" mode in which the usual constrains of the enemies initial state are lifted, and/or in some cases, the detection range and radius is increased. in the case of the FPS, the biggest giveaway that the enemy is in state two is if the enemy is triggered, but the player works their way around behind the enemy without the enemies triggered state being switched to active, in which case the player can stand there, right next to the enemy while the enemy cowers behind a wall seemingly waiting to be set to active.  Some games try to ger around this by giving state 2 enemies both a fixed range of far-sighted triggering, and a close range 360 degree "proximity trigger" that alerts them to the player being within melee distance.

Active / Queued active
In the final state, a set number of enemies will engage with the enemy with their full skill set, supportive skill set and higher level defensive skill set, this is the real killer for AI processing on the CPU, and why most games give that effect when in large mobs that only a set number will actually attack at once, unless the enemy is such a basic ai that attacking until its dead is the only skill it has.

To break it down further, in the former instance, you will see, and any gamer worth their salt will have encountered this, groups of enemies ready to fight but just standing there letting a small number of them actually hit the player, then engaging only when that active enemy has fled, or died.
The latter is a case of not really being in an active state, but rather being in triggered state but set to attack within a set proximity to the player, basic MMORPG's from back in the day would use this on basically all aggressive enemies, Ragnarok Online is a great example here, you essentially have two states,  idle > triggered (idle until hit by player, then follow player and attack when in range)
idle > proximity triggered (idle until within range of player, follow and attack when in range)
These two routines are basically the same for all enemy types, a poring that can only attack when within 1 cell of the player and a skeleton archer who will attack from 15 cells away, is the same just a "engage distance" adjustment in their scripting, if we look at the skeleton archer of having two values,  trigger radius: 20 engage radius: 15, then if a player is 21 cells away the enemy wont see them, if the player goes within 20 or less, the enemy will detect the player and move to a radius of 15 or lower and begin attacking, likewise if the player flees but stays within the 20 cell radius, the enemy will continue to follow, but running 21 cells away will set the enemy back to idle.

In the example of ragnarok, this is not real AI, this is just scripting triggering, in most games, *ESPECIALLY* musou games, both states 1 and 2 are just scripted triggering, state 3 is the only instance where an actual AI takes over, and the number of active AI combattants is low. most large mobs in musou games actually use an updated version of the ragnarok method and conserve actual AI routines for bosses and special enemies.

Network stacks
If you are running a WiiU game, the network stack remains active, because it has to, regardless of if you are playing online or if the game even has an online mode, because the WiiU SDK is setup to allow deep integration with networking, just as the PS4 and Xbox One are, while multiplayer can and always will use more resources to function than the framework for network functionality, it isn't the network stack that causes the slowdown, what causes the slowdown is the client setup, the game is set to make only a set number of enemies use active states at once in single player, in multiplayer if someone engages an enemy far away, beyond the scope of the players field of view then it won't impact the performance of the players client, even though the actions being done by the other players are still happening, however if a player engages enemies within your field of view while you are doing the same, the number of active AI has to double for each additional active player in the world within range, simply because it's actually LESS of a strain on the console than having every single pawn on the field at once reporting its position, health, state and proximity to another player, over the network and syncing to every connected player.

So instead what you get is active AI being handled by your client for enemies someone else is attacking, the only information relayed to you from the other connected clients is the player actions, player state and the death state of an enemy, this is then handled clientside.

This is why someones a connected player will do a finishing move that should definitely have killed the enemy they were attacking but the death of the enemy is delayed slightly, because your client was controlling that enemy up to the point where the network told that enemy its dead.

the real killer here, and the reason for the slowdown when playing multiplayer, is the additional active enemy load - if you just follow someone around but avoid engaging with enemies the performance will stay relatively identical to singleplayer, but if you follow two people and watch them engage, or engage yourself, your client performance will suffer because its now processing more than it has to do when playing solo.

AI is not a good indicator of CPU performance, because AI isn't as active as people often assume, and at the same time many people don't notice or understand the subtle but clear differences in states, or why games use trickery to keep the performance hit down, as such the best AI in a game can do is gauge how well designed a game is, in the case of hyrule warriors, the online play performance hit suggests they knew of the downfalls ahead of time but opted to leave the number of active pawns where it was to make the single player experience a little more fun.

Oh and for the record, on ragnarok online you can walk in to a town with 1000 active users at once, performance will take a nosedive - that isn't because theres 1000 players and your network is struggling, that's simply because the game has suddenly been asked to draw a 1000 users each with a different sprite group, the way ragnarok is set up is for a base sprite, weapon, head type (inc hair), accessory, mouth-accessory, and hat. that's 6 sprites to make up each character, so 6000 sprites on screen at once - rendering is what causes the performance hit here, not the network stack.

In accordance with being transparent and giving full disclosure, prior to my resigning, I worked on an early version of Hyrule Warriors back in 2013, Wind Waker HD, and on the networking side of Mario & Sonic Sochi 2014, and another Nintendo game which puzzlingly has yet to be announced so has either been pushed back or cancelled, though because of NDA's I can't discuss the development of these for obvious reasons.

I actually reviewed Hyrule Warriors for the website I work for. After I finished I realized I didn't talk about the graphics much. So I added a paragraph about it.

For me personally, the character models alone show the wonder detail and power of the Wii U. Then you add the stages, and cutscenes, and attacks, and it's all beautiful. And this is just for Hyrule Warriors! Imagine what Zelda Wii U will be like!

If anyone is curious as to what I thought about Hyrule Warrior (hint: It's great!), check out my review!

http://www.followingthenerd.com/video-games/game-review-ftn-review-hyrule-warriors-for-wii-u/

Ok. 'the Wii U's CPU isn't THAT weak' is not the same as 'its super powerful guise!' But frankly if you aren't making a claim that it's a powerful CPU you are then just claiming that no the CPU isn't really crappy, its just kinda crappy. 

I agree. 

What I'm claiming is that the myths about it just being 3 Wii CPUs taped together are just that, myths. 

Nobody actually ever truly believed it was 3 Wii CPUs duck taped together... People just say that because the system is greatly underpowered compared to the other 2 consoles. The same as when the Wii came out, where it was 2 GC CPUs duck taped together...

Hence why I asked why you feel like it's a good idea to stir that up now. 

I'm not stirring anything up; if people use this as an excuse to troll, that is their fault, not mine. We should be free to discuss these things in a mature manner without having to worry about people being asses.

You are. You play in hands of those trolls by bringing this up.