Would of been so easy to have done an ulduar style T11, making the fights just seem, more epic. Not a simple switch, but something you have to strive to activate. Would of lent a bit more credence to this raiding tier imo (along with having 25 mans being the mandatory way, instead of this 10 vs 25 crap)
Magmaw - normal version nefarian would help you kill magmaw (an annoying pest to him). heroic version, you shoot nefarian, fight turns into him in the air reigning down destruction +you have to kill magmaw with no help.
omnotron - all 4 versions would of been up at once, instead of 2. normal version you would shut down the "old 3rd one", but in this "heroic" mode, you would avoid shutting any down.
maloriak - would of been simple enough to break black vats part way through fight to trigger the slimes, and also increasing dmg of maloriak.
atramedes - you would start the fight by using X number of gongs during a 5s interval, driving atramedes intro a frenzy.
chimaeron - one version with the save-bot, one version would of been without the save-bot
nefarian - probably would of been the biggest rewrite, but would of been so epic. onyxia would only be in the hard mode. in normal version, you kill him before he can summon onyxia (pushover during summon interval would be easy). in hardmode, you would stop dps, let him summon onyxia, then kill both.
conclave of wind - normal mode you would fight on different platforms. hard mode you would lure to be on same platform.
al'akir - not sure
halfus - how many are released would determine normal vs heroic. typical add vs boss. freya 3 copy.
valiona - dragons both ground, both air at same times in heroic. this would be done by engaging both with a tank to start to the fight.
ascendant council - Each of the 4 bosses would have "X" health. Normal mode, you would kill one, leaving the other alive, as once you deal 1.5X health in p1 and 1.5X health in p2, the "survivors retreat". In heroic, you would dmg each to 25% instead of 1 dead, 1 50%. This would determine what abilities the monstrosity has.
Whether the boss is water/earth, water/air, fire/earth, fire/air, water/earch/air, fire/earth/air, ect ct ect, fire/water/earth/air would also determine loot.
Cho'gall would be a "simple" dps race to "get him to 25%" to stop his closing of sinestra's portal before he closes is. if he closes it, last 25% is easy. if you manage to stop him in time by getting him to 25% before timer runs out, sinestra empowers cho'gall, making the sub-25% phase......a lot more fun.