Have you completed Mechonis Core? That's where, I feel, the story really kicks up again. Agniratha sorta just re-starts the plot after a lull...

If you don't like that, there's no pleasing you it would seem :P

Today i learned that i'm much better at leading the group with Sharla than Shulk, and in turn much better with Shulk than Reyn.

And did my eyes deceive me, or did that tentacle-mechon-boss change level on me several times in the course of the fight? I swear i saw it range from 17-20, going both forwards and backwards.

You're correct. Most bosses in the game use an aura "Last Stand", where they cast Haste, Strength Up and increase their level by 3 when their health is below 15%. 

And Shulk is the best character to control IMO. Sharla heals well, and Reyn will topple when you break. Only difference is, you can use Back Slash/Slit Edge/ Monado Arts when you choose, and when it's most effective.

I've completed Mechonis Core a week ago.  Right now, Junks is sitting in Colony 6 just waiting for me to make another visit to Bionis Lung. 

Interested to see what twists await in the ending...

I don't know, the story at that point just had me totally unimpressed...  The whole Xanxa, Dickson, Alvis thing was pretty lame.  The last time the plot had a surprising moment was when it was discovered that Fiora was one of the Faces on Prison Island.  After that, it was all down hill.  But I'm really hopeful for the ending after Soriku's tease.

A lot of people around the net seem to like using Melia.  She's a great character, but Shulk is way more fun to play with in my opinion.  So much fun hovering around the back and sides of enemies on going to town with Backslash, Slit Edge, and Air Slash and actively intervening with Monado Arts after seeing the future.  So much fun!

Right, that was the only thing i was thinking of. The CPU might be better at predicting who's going to need to be healed one second from now when the next round of damage comes in as opposed to right now. I'll have to test that, i guess :/

Melia is the best character. Elementals for massive damage and buffs, Spear Break+Starlight Kick for insta-Topple, Aura and Arts seal attacks, slight healing, ability to chain to almost anything...she's so cool. You've gotta love her!

In addition, the ending cutscenes are cool, and very out-of-nowhere. But if the plot twist about Shulk being dead from the start, Dickson and the diciples didn't please you, I don't know what will! The only thing which surprised you was the most obvious thing in the game IMO!

It's best to play as all the characters when you get them, namely to get their 100-Art achievement, but also to experiment with their playstyle. See who you like. I personally like Melia the best, but you won't have met her yet (just don't ignore her because of bad HP and defence!), so it's best to stick with what you know. All characters have advantages and disadvantages to playing as them. So just see who's the best really. And, of course, mix things up to boost the affinity chart as well!

Also, Sharla doesn't chain well; at all, and her attack power is the lowest and the slowest of everyone in the game. Be wary of that. But as a healer/support, you can't go wrong with her, and, of course, you can heal/protect people who have the aggro, whilst the AI will do that to the people who have the least HP, and also the people she shares the deepest affinity with. So, pros and cons.

Bird Lady is awesome to control. But her learning curve can be off-putting for some.