The problem is that groups in dungeons just aren't going to wait for the slowpoke warlock to catch up, they are going to run at top speed all the time, which means you're going to "underperform" on trash packs, and keep people waiting to pull bosses, and all this just makes warlocks less desirable. Unless we're top dps, which we aren't. In fact you're going to get the inevitable "sorry your dps is too low we have to replace"
I actually got that as affliction on a Archimonde pug because they wiped in about 30 seconds on the first pull and well yeah there were the huntards and mages at the top having blown all their cooldowns etc and me at the bottom of the barrel because of afflictions rampup times
So it makes Burning Rush mandatory, so you burn through your health to keep up and bug the healers. You can't pop the shield the mitigate that because they are mutually exclusive and you can't switch talents either
Being "viable" just makes me think of the kid who gets nothing but C's on the report card with remarks like "adequate", "tries hard", "average" or..."struggles to keep up"
Who wants to be that?
I had hopes for affliction, particularly when the devs went out of their way to hint that the complaints about affliction's godawful aoe and lack of burst making it a third wheel in certain encounters had been heard
Okay, no spec can be good at all, but that's going to hurt a lot more because the time you'll have to invest in your artefact makes spec-switching a lot less viable.
Indeed, one might almost think it's just a gimmick to act as a time sink, to get progression raiders to double-level the artefact power crap