The other night a Guildie was trying to heal for these 3 guys in PvP gear trying to do HM Last Emperor, they spent over 4 hrs in there and these pvp player kept complaining about how hard Bioware made the instance....

 

Moral of the story, don't PvE in PvP gear...

I think you have it wrong. I'd suggest that (massive generalization incoming) players who enter PvE content in full PvP gear are more likely to be those who haven't done much of the end-game PvE content (else they'd have some PvE gear, right?). More likely in the case you've highlighted there its a problem of not knowing the mechanics rather than gear being a problem.