Personally I kinda like how champions are in 0.77
Its the coolest when its just 1 Sovereign + 1 or 2 backup champions ... once you add more than that it starts to feel a bit cheesy ...
although I dunno, maybe its just because on both my normal games, on normal settings (medium map), I've only met another nation once, (albeit I slaughtered him after about 20 turns), and I was fine with that.
Its really fun just having 1 or 2 champions + a few units go around doing quests. I know I've suggested that only champs should do quests, but honestly the units don't feel forced (maybe because its 4 soldiers instead of 40).
Early on EVERYTHING matters. Each spell matters as if life or death (because you don't want injuries on champs ... or at least I dont
)
Get every ounce of help you can from Dog summons, Clay Guardians, etc (about the only thing I didn't use were the food items, but I certainly COULD have a time or two ... things got really close) -> I also never used the whistle, but honestly its better to use the food items/whistle early on because later, once your a powerhouse, saving those items don't really matter.
Champions are definitely NOT OP until you level them ... and until then, they are 'almost' as weak as they were in E:WoM
therefore you sacrifice your units, mana, everything in the early game in order to get them leveled. This feels about right to me.
Also, just from a 'coolness' perspective ... having more than 2 champions in an army starts to feel a little crowded-> other peeps crampin my combo-style I have going on.
Btw though ... WHY is there a 23 strength, 11 intelligence champion (great for melee) that has all skills focused on CASTING!?
Ultimately he helps with an extra haste or two, plus my only form of 'slow' ... but by late game I may as well just cast haste(self)+fireball ...
as im still learning the game though, I leveled him in water spells to see what is available.
WHY no earth tactical spells? Why is it all strategic? Why is freeze!!! (awesome water spell) NOT TACTICAL!? 
I can understand Whirlwind being strategic only I guess ... but for the love of tactical, why not a temp. stoneskin for tactical and maybe another version of tremor? (only because they have no tactical, and it seems a bit silly to imbue a champion just so that they can raise and lower mountains.
Cloud Walk is AWESOME! (completely worth Air Archmage even if Titan's breath is a bit ... yea. Titan's breath would be a lot stronger if movement wasn't so fast, but knocking down is cool ... even if I could just, yanno, KILL them for the same amount of mana. It doesn't do damage why? not a lot of damage, just 1 or 2 damage to show it did something, other than delay the inevitable (one way or another)).
one cool story though ... Yoske was a crappy 3 strength merchant when I picked him up, and now he is an awesome hero with 20-30 strength or so. I know he is my strongest unit because I have him using the Maul I got from an Ogre(or wassit troll?). +100% strength bonus is really, really nice.
Bezerker's Axe would of been better if one of my champs had some extra source of accuracy (maybe I just need to wait a few levels), but for now its basically the same thing as Double strike. It will hit twice, then miss. One time, once, it hit 3 or more times.
If accuracy does go up with level though ... maybe it will eventually be awesome (and worth its value in gold).
I don't mind how fast the units go up in Stats ... and even WITH a max move Champion, sometimes the fireball wins first 
So I'm not sure what the answer is. Maybe only limit movement (or remove charge at least) to regular units.
Or maybe just better Tactical AI (using counterspells I guess?) ... or maybe for the AI to be competitive their 'large scale view' is the thing that needs the most work.
Its easy to say one strategy is weaker/stronger than the other ... but it seems like Sky's the limit with all strategies, and that the early game is the most critical (for keeping champions alive, being able to complete quests, defending cities ... I guess defending cities could always be a bit of a struggle, as your mega-stack can only be one place at a time-> ignoring cloudwalk for the time being, that takes some serious investment to get to)