*Sigh* and now we enter the PvP gear vs. PvE gear issue I've seen way to often. IF you're wearing full PvP gear and attempting a hard mode operation, that's your problem right there. Especially if the rest of your raiders are doing the same thing. Run the others in normal mode till you can replace that PvP gear. (The expertise stat does NOTHING for PvE content whatsoever). Not sure why people think high level PvP gear will hold them through hard raids.
*edit* Oh those other stats like power, surge etc, are actually better on the raid PvE gear than your PvP gear.
Have you even seen the stats on end game pvp and pve gear? They are virtually identical. PVE gear has a tiny bit more to your primary stat and endurance, whereas pvp gear has the pvp stat.
A tiny bit less endurance and aim isn't going to make it suddenly undoable.
Also, champion pvp gear is massively better than normal 50 instance gear. Learn the game before you post like you do.