I played around with affliction on the PTR without an artifact weapon, and I really liked the feel of it, but I'm a little unsure of how the artifact weapon talents will factor in to end-game. I noticed that on most class/specs, the artifact talents that are bordered in gold (including the initial talent) pack a little more punch than the rest. Maybe they'll deal exceptionally high damage, but on a cooldown, or provide an on-demand buff, or a hefty proc based on your normal rotation, for example. For the afflication lock, three of the four abilities require killing targets.
One of them is wrath of consumption, buffing dot damage by 2% per kill, capping at +10% damage for 20 seconds. Another is Soul Flame, causing killed targets to burst for aoe damage. The initial talent, Reap Souls, requires sacrificing souls captured by your artifact weapon (from killed enemies?) for what looks like a pretty solid damage buff of +10% damage and double all artifact traits.
Does anyone have any good speculative thoughts on how this could effect end-game raids or mythic dungeons? I'm a little unsure myself, about committing to affliction lock and leveling the artifact weapon, only to find that viability is only there when a boss has sufficient adds to make affliction work like it's supposed to. I can see it making sense to balance affliction around the fact that they have +20% damage and double artifact trait bonuses, but then I can see situations where they get none of these for whole boss fights.
Beta Affliction Artifact Calculator