They upgrade the engine continuously. Don't confuse the style of graphics for the complexity of what is displayed. Their spell effects can be pretty involved.
WoW's
visuals may be involved, but their graphic engine is old. No getting around it. Blizz implemented a better graphic engines for D3 and SC2, but they haven't updated WoWs all that much over the course of 10 years. The game is made for bare bone graphic cards (hi2u2 HD3000?). Blizz
did start trying to update WoW in Cataclysm and a bit more with MoP, but not all that much. Definitely not enough to make the 680 in the iMac break a sweat.
And yes, I play at native resolution of 2560x1440. But like I said, I don't play with Shadows on (never have and far too lazy to care about it). And I
always cap my fps, since there's zero needs for more other than epeen and MoP introduced a bug with graphic cards in that they can get burned out. Fun times! D3 is also played at the highest setting, which was a little surprising the first time coming from the old iMac. Hell, it took me about a week to not get nauseated in WoW due to how stupidly smooth it ran vs. what I've been used to.
SC2 was getting 103fps with every maxed out for the first 3 or 4 mission thingies you get with the basic starter edition, but since I don't know squat about how to play that game nor care, it doesn't really affect me.
Some people have random lag spikes or crashing. I have no clues why, but personally even on my old iMac I've never had a single issue with the game, minus WotLK, in the Howling Fjord where there's a forest that's all red and on fire... yeah, that area made my old iMac cry. New one, not at all.
Also, far as the editing to force the opengl thing. That's been gone since WotLK-ish, early Cata.
