So Affi is getting some changes that will make for interesting burst window set up ..
Drain Soul is going base line and its damage lowered because in its place we get a talent that has DS increase DoT damage by 20%. Now look at Rot and Decay on PTR and you will notice that only Drain Soul triggers it. Lastly I see synergy between those two talents and 'Contaigen' which buffs all damage on targets affected by Unstable Affliction.
So we lose sustained from Writhe Agony but gain burst via Malefic Grasp+Contagion. As for play style I think Drain Life is relegated to only heals and we burst as usual (bank all the shards and dump full DoT's+all UA on kill target and Drain Soul) ...
Looking forward to seeing numbers on:
Writhe Agony Vs. Malefic Grasp (+ Contagion)
Sustained Vs. Burst (+ Absoulute Corruption)
Edit: I just noticed 'Drain Life' has been removed from all talent tooltip (Artifact / Spec / PvP) and replaced with Drain Soul ..