Lib on legion is probably one of the most amazing things I have ever seen. You think drk is unstoppable with Rag and Apoc 99? With the potency on drain and other absorb spells you wont need the cures from cata... Honestly the way I look at it is Lib is just a sick way of combining the two weapons that make DRK so unique. On the off hand Libs Oat-trice shits all over rag....
None of this is really backed up by math..
We were talking specifically about Conqueror as a MS weapon, in which case my comment was directed towards a question of whether it really even beats MS Resolution (which under zerg scenario it likely doesn't due to massive TP generation).
As for a general DD piece, I don't even see Lib beating Ragnarok. Furthermore, if you're stopping to cast drain, you're doing it wrong (from a DD perspective).
Conq doesn't really give you much DD (if any) over Ukon/Rag. Liberator doesn't give you more DD than Rag, and doesn't provide for more Survivability than Apoc..
But I'm happy for someone to correct me (with science!).