World of Warcraft PvP versus PvE?

Ever since cata came out and moved back to the old vanilla style of hard mode raids I've noticed a lot more people moving over to the PVP ranks but staying in there PVE gear, Im in full vicious gear right now and I having no problems with the PVEers, but do I have to worry with tier 11 people if ever I do run across someone in that set?