The problem with Skyrim isn't that there's too much of it (like that's an issue for a good game like this), but rather the balance.
Illusion becomes worthless at higher levels, even with perks and dual-casting and before that it's simply broken: you can just perma-charm your way out of any trouble. A bit too many extremes if you ask me.
Some perks are just useless outright. Tell me, why in a world would I take any perks in lockpicking if already at level 30-something I can easily crack master locks open without much of a problem. Not to mention the fact that there aren't that many locked instances in the game and the ones that are, mostly have crap. The only perk here that would've been kind of nice is "Treasure Hunter", but it costs a total of five perk points to get. Considering Skyrim is more of a leveling RPG than equipment hunting one, seems like kind of a waste. Better put points in smithy and enchant, if you're a warrior. Mages should do without any of those since they (in my case "us") have Morokei mask (100% mana regeneration increase) and Archmage's Robes(15% mana usage reduction, 100% mana regeneration increase and +50 mana), unless you want to break the game by getting a 100% mana usage reduction by crafting stuff using the enchant perks.
I don't really get how conjuration can break the game, at least for now for me. I use Destruction, Conjuration and Alteration all the time. Conjuration is a good support, but it's mostly just a cover for me while I throw fireballs at 'em. Could change in the future though, Frost Atronach is pretty damn powerful and it's only a second one and is without the Elemental Potency perk (50% buff, don't ask in what), pretty useless in boss fights still.
Oh, yeah, AI still sucks.
EDIT: a semantic error about Frost Atronach.