I beat Titan HM as a BLM. Of course your dps is going to suck if you are told to meele titan to build TP for LB2, as in my case.

BLM also have access to Virus which is nice for phase 3 Tumults.

Is it more difficult to dps, sure, but its more then doable as a BLM.

Phase 3 is more about survival then dps, you can't dps with your face on the ground.

So in short, BLM don't suck for Titan.