How are you pulling mobs?
My lvl 49 lock can send in his voidwalker, apply Corruption and CoA once the pet has used his first taunt. Then I use Immolate and wand down the mob.
I don’t seem to pull aggro until the mob is already half dead, and by the time the mob reaches me, it’ll already be so low that I easy face tank it or it runs away if its a humanoid.
The only times I pull aggro from my voidwalker are if I start dotting before he reaches the mob, if my voidwalker is OOM and can’t taunt, or if the mob is a higher level. Besides that, just give your pet a few seconds to reach the mob, open slowly with the instant dots, and then finish with an immolate and wand. You’ll be fine. I usually send off my voidwalker to attack the next mob as I’m finishing off the current one and looting it. That way I don’t have to wait much time before my pet has already started attacking.
P.s. I’ve also done the drain tanking method with the succubus and it works super well. I think I like that method more when grinding in certain spots but I haven’t exactly figured out when I like it more.
BTW, playing as Affliction spec. It works well for me and it’s definitely my spec of choice when I have those WPvP encounters. I don’t claim to be a warlock expert though