Access to silence and stuns is fairly important, even setting the obvious issue of PvP balance aside. PLD was essentially mandatory on certain fights in ARR because of its ability to provide both a silence and an on-demand stun. The most obvious solution to this is to avoid designing wipe mechanics which mandate chainstunning an add or silencing a particular attack. While this mechanic type has thankfully become fairly rare, it occasionally rears its ugly head (this raid tier included). If you're pugging a6s and you don't know/trust the brd/mch, you're probably going to swap out to PLD. Wiping to spaghetti and waiting on cooldowns to reset because someone was too focused on their dps isn't a good time.