Yes I feel the same way: when I virus on Titan's MB > tumult combo on BLM, I feel that I take way less damage from the tumult as well.

Then again, this could be because the healers are freed up from having to use emergency measures on tanks so that the mitigation-based healers can lay down all the possible mitigation (like soil and succor).

If I might ask: where would be the perfect place that you'd test this? I guess ideally you could get a bunch of people together and just do Titan Ex's phase 1 over and over again like Cel suggested. You'd need a decent sample size, though.