Interesting, I feel like purge is smoother. Are you running your tainted setup with extensive pre buffing? Or is this a comparison between good to go setups, which can start the game right away?
I've done tainted setup with and without prebuff but its only a few extra clicks for a full game since I never have to respawn them normally. It's a pretty substantial damage buff for just swapping rings/ammy/boots/shield, though rearranging charms might not be worth the effort for +1, nor trying to get a +6 dagger over mang songs.
The minimal prebuff is just so smooth its worth doing for TZ, while if you were grinding some fast runs like chaos or baal you wouldn't bother
I'm still on the fence about physical vs purge ES, and I haven't tried purge with extensive prebuffing yet either. Just standard obsession/meph/gheeds/slings/etc.
It does feel like the purge setup lacks both sustain and single target DPS for bosses / heralds. Its still reasonably high dps against them, and you still have an insight merc, but you don't have lifesteal, manasteal or hex siphon's LAEK/MAEK.
But it sure does comparable aoe damage to the 3.1 ES warlock, shredding everything in a couple chucks. Still, noticeable when you clear chaos fast and then reach diablo and have to grind away at him significantly slower than the other builds.
I don't know how a prebuff setup would compare for that