it's possible, but it doesn't necessarily make the run faster to play like that. Especially as a PLD with no AOE its' often faster to just let the DPS take a mob so you can do less Flashin' and more DPSn'. Flash is basically a DPS loss unless the added mitigation lets your whitemage do some more DPS as well.

Enmity isn't your resource alone to handle either. DPS should know that they do more actual damage taking advantage of a tank so that they can use flanking combos and the like. If they decide to be stupid about it and just go full ham and rip hate they're the ones actively hurting their DPS, not you. It's not that damn hard to switch targets mid-fight: I do it constantly, so why can't anyone else?

You're the tank. You're 1/4 of the party. Don't let crappy players dictate how much weight you should be pulling.