We'll see. But with the possibility of a weapon swapping mechanic significantly increasing dps, and the recent experiences of rogues and balance druids, experience might tell us that they won’t view this as “fine” for very long. It is somewhat counterintuitive to use your “burn phase cooldowns” (haste pot, PI, bloodlust) at the start of a fight in order to do the best possible dps in a burn phase that actually occurs several minutes later.
I dont see how weapon swapping will work in this case, since it is the eradication procc you are waiting for to pop haste buffs, and waititng to get eradication and weapon procc at same time will ofc be very infeasible (remind me if I am overlooking something here, please). So I don't see us locks using weapon swapping mechanics any time soon. Engineering however seems to have become slightly too good for affliction locks, assuming the mechanics stay as they are right now. On a related note: I always see ppl saying that one should ask for PI, but I was under the impression that PI does not stack with other haste buffs - again pls correct me if I am mistaken.