This pretty much sums up my sentiments perfectly. For me I've never played in a game before that even allowed you to separate RP from PvE as far as guild was concerned, and most of the best RP I've encountered came from doing Guild based RP events. For me, so long as you don't care about rushing through content, I see no reason a group can't be an RP Guild and still be a functioning PvE or PvP Guild as well. In most cases, raids take place one or two nights a week, which leaves 4-5 days in the week to RP whenever you want.