I've never been much of a fan of POWERFUL wizards or characters/heroes in these games anyway. What they end up doing is if you lose your main POWER character the game is OVER.
Well the intention for this game is that you lose if your channeler dies. So if you hoard all your essence for your channeler to make a "POWERFUL wizard", and then lose him you literally lose. Unlike where in HoMM where it tries to pretend the game isn't over yet.
I'd rather not see the heroes/wizards specifically get experience or gain levels. What I would rather see is the power be determined by artifacts discovered or artifacts built/forged. This way if you do lose a hero or wizard you still have opportunities to build another one back up by mfg new artifacts or discovering new or better ones in REGENERATING dungeons/crypts and other explorable areas.
Too many of these games MOM included have a definite amount of ability to gain experience or item loot in the explorable areas. I propose that after a number of turns after some dungeon/crypt etc have been cleared that they regen with new creatures and new items, sometimes harder sometimes easier but never the same thing twice.
But this is built off of a potentially flawed assumption. You assume that the world of Elemental will be as static as in most other games. But from the little snippets of information we've been given by the devs, the world will probably never be free of wandering monsters, dungeons will regenerate, etc. If you invest a lot in a champion and then lose him, you should be set back. This can be done without leading to HoMM-like situations - in HoMM it happened because having one super-hero was by far the best strategy. All they have to do here is make it just as viable to have more lesser heroes. Then it's the player's choice whether to put all his eggs in one basket or to spread them out, and thus it becomes a strategic decision.
I'd rather see battles won by strategy & tactics than by MY hero is greater than your hero so you lose.
But in this game, whether or not to concentrate on heroes at all, and then how powerful to make them, is probably going to be a strategic decision. They've already told us that their intention is to give the player many viable ways to play the game - including to forego heroes, or to rely almost entirely on them. For two roughly equal players, if one has a more powerful hero than the other, then the other likely has something to make up for it. At least, that's the goal.
Read some of your fantasy novels you don't see any of those characters getting so powerful that if one was lost like FLINT in War of the Lance that there was no hope of the good guys winning. Only really Raistalin (sp) gained more power during the story, but, still he wasn't powerful enough to win the war for their side.
There are so many examples of stories that rely on an individual character's survival it's not even funny. The Sword of Truth is the first that comes to mind. It's there in LoTR is a few manifestations as well (if Frodo died it'd have been over - without Gandalf Sauron would've won, too). The Chronicles of Thomas Covenant. Give me more time and I'm sure I can think of many more.
It should take the WHOLE team, the WHOLE army, the WHOLE faction to win not just one overly powerful character.
But if a player chooses to make his WHOLE team his one overly powerful channeler, why not? That is his whole team. He'd probably have some small army to back him up, but why prevent people from making that choice? As long as making your channeler incredibly powerful is no more viable a strategy than building up an actual army or heroes, there is nothing wrong with that.