The only time I have seen a delay is when I reach a new region in a realm and the first time I check my map afterwards, it takes half a second longer because it's showing the map filling in from the previous white background. When I check the map after that on a region that's already filled in then it's instant, at least for me. 

Finally finished Ragnarok and my god, what an experience!!! It surpassed the 2018 game in nearly every way, except two. At least for me.

I'll put a spoiler tag just to be on the safe side

Nitpicky stuff for sure but didn't take away from how much of a masterpiece this game is! Well done Santa Monica. Hopefully I'm not the only that shared the 2 frustrations I expressed in the spoiler tag and is something that can addressed and improved upon in future SSM games. 

While my overall enjoyment level for the 2018 version of God of War was arround 4 or 5 (out of 10), for Ragnarok it's arround 8 or 9.

The major drawback for me is still the combat (outside of boss battles), because I don't find most of Kratos attacks interesting, and in a lot of instances I heavily dislike the combat design where they constantly and intentionally spawn enemies behind you, no matter how many times you kill them to get them off your back.
I want to make use of some of the moves and combinations you can do, but it's not really possible when in the middle of it, a red arrow appears behind you and Mimir screams "Behind you. brother!". It happens so often, and it is definitely intentional, as I tested it in the training grounds.

Luckily even though I don't care about most of Kratos moves, there are other characters who have more fun playstyles that I do care about in this game, unlike 2018.

I found myself sitting on 47 000 EXP points for Kratos, because I'm just not excitred about upgrading his skill tree further.
The only exp number I'm interested in is my partner's, as I do want to grow their skill tree for now.

I'm referring to

They did make Kratos, and combat overall, a bit more fun than in 2018.
I like his Glacial Permafrost skill for example (which causes beams to shoot out of your attacks), and they made parrying more interesting in this game.
Shield Striking blue-circle attacks also add a nice flow to combat.

In 2018 I felt like the game ended right as the story was getting really interesting.
In this game, I feel like they are continuing that story from the beginning, which has made the whole journey very interesting to me, story wise.

And side quests are a night-and-day improvement over 2018.
They have worthwhile stories and rewards in this game. In the previous game it was usually just a random fetch quest for a spirit, and then you got a little conversation.

Mini-bosses are also heavily improved in this game as they don't just cycle through the same trolls/golems for the 1000th time like in 2018.

I'm currently 25 hours in, and just finished the side quests in Vanaheim.

Yes the enemies in the back is something I don't like as well. Seems to serve two purposes the break of you combo and making you need to turn around a lot (for me mapping the 180 turn is pointless, but that is their expectation), also they want you to be moving around and changing enemies instead of focusing it seems.

Another thing I don't like is how pointless the target lock is on bosses and sub-bosses. They have a lot of moves that are teletransportation that make they go away of your screen (besides the challenges with 2 or 3 of thoses special bosses where if you are locked to one invariably the other one will come at you and your counters will de dampened due to the lock).

I have upgraded and mastered all trees for all chars and also several of the rune attacks even if I use very few of them =p

On your other points I mostly agree with you as well. But I would say I have liked the game more than you.

I'm only 2 hours in, but first impressions are great. Plays and looks great.

It get much better after the start so if you are already please you will likely enjoy it.

Personally never had any issues with enemies from behind, I am constantly running around engaging enemies so I rarely stay in one place for any length of time. I will say one of the reasons why I do not play on the harder difficulty is not that its hard but because regular enemies power through most of your abilities which does not make it fun to play so I can see where that is a problem.

For Bosses, I rarely use the target lock but that is because I am always initiating combat and rushing towards them unless they are doing their teleport thing. I spent a lot of time in the training area using different moves to see how effective they are and always looking at moves that juggle the enemies where you can get the max amount of damage.

I also have upgraded and mastered all trees for all weapons which is where the training area really helps especially getting into your fire, frost or stun abilities the quickest as it helps to dish out more damage in a short period of time.

I fully expect to enjoy the game.  GoW is up there with Souls, Zelda, Mario, etc...  never been disappointed.  

Perhaps you could try regular mobs on balanced and increase difficult with bosses or on the extra bosses =p it is possible to get combos on the bosses if you have good reaction.

I know that the arrows helped me a lot because I was playing most encounters throwing axe =P

The mastering I got most of them while normal gameplay and trying stuff out, but when I was close to end to improve my damage for the trials and challenges I gone to that arena and done the other mastering.

You can definitely get combos on bosses no matter how hard, as long as you know their stun window and what stuns them.  You cannot trade with bosses as they will nuke your health so I only use my special abilities when I get a stun or shield parry.  All bosses have that stun gauge at the bottom of their health bar which I am constantly looking at for when I can unload all my abilities using all my weapons without them jumping away or trading blows with me.  

I usually only play the harder difficulty when I max out a character in New Game plus when I can use all my abilities, armor etc.

Yeah, the moves you use a lot you will quickly master.  Other moves you will just not remember which is what usually happen with me until I get a chance to just spam them in the training and see how best to use it.  Mostly I am looking to see how effective the move is based on different enemy types.