If you are looking on topic it is exactly true... He can't get better pve gear so he uses pvp gear to get his GS and hp up.
I was just saying if it was ME who was raiding the lead I wouldn't invite him.
But as he sais, the only thing they look at on his server is GS and HP, So the answer is:
yes you are fine with pvp gear, and no you shouldn't take wrathfull over relentless, since it is indeed 3 times as expensive so it would take a lot longer to gear up. If you allready got 40k unbuffed hp you are fine to tank icc10 and even icc25 man...
you will be sitting around 55-56K hp raidbuffed and with the icc buff... So if you can hold aggro you are fine
Maybe give a armory link if you want some more info!