well, as PP try to find more open minded party, its true that PP cannot buff whole party at once, but is that really a problem if u are active prophet? u can distribute buffing each member in 2 mins span, that means u will never run out of mana but also there wont be ever guy w/o buffs
also most of parties need boxed pp, if u find decent pt, why cannot they box WC to just buff as they would do with prophet? where exactly is the difference in that? yeah, WC is insane in pvp, but so is active PP whith his decent heal, 1 more ress (eventho its low % ress, while fighting wars the loss is so little ppl ress even with normal scrolls, so i dont see problem with it), u have mystic immunity which is really good, mass fear (idk the landrate, but i saw some prophet olympiad video where he used it almost all the time and it was landing always [even on dagger which used hide and got dehided by it], but thats w/o mental shield), it has root with pretty good land rate (should be, not confirmed)
as i said, its just about what ppl u find to play with, sometimes meta picks are way overrated and ppl think they cannot be replaced (speaking for myself, i would rather have active person which enjoys playing PP than to force him to reroll to WC and he wouldnt enjoy the game, that would lower his performance as well)