I could beat Titan naked with a ghost costume. That doesn't mean its a good idea.

If you are below Relic+DL, you are likely getting carried and you will start feeling the lack in throughput significantly by Turn 4. You won't pass Turn 4 with an entire group at ilevel 60.

It has nothing to do with "taking damage", if you take direct damage in Coil as a healer - you are probably dead. Everything is going to hit you really hard, even if you roll in with full ilevel 90. The concern is with throughput. The carry is best handled through DPS or Healing because you can end tough mechanics faster and have the ability to pour on huge heals (normally would be over heal).

Your gear for Titan is fine. People grossly overestimate that fight. I did it without a single DL.