I don't think it is elemental damage across the board. I think it is fire. Companion healing is irrelevant as we are talking operations. It is not something I can document with logs, as I don't keep logs very long. They tend to fill up my computer.
What I have noticed is, while in Dxun operation, I can handle everything up to the 3rd boss fight. One of the trandoshans uses a fire attack and it almost one shots me. I can survive it with a cool down...once. I would think fire would be similar to acid, which Red casts. The acid hurts, but is no big deal when you have a decent healer. The same boss can be fairly easily tanked by a Jug. Mind you, I am wearing 306 set bonus gear complete with new augments. The Jug is wearing 296 unaugmented gear.
Are we to assume amplifiers are required for story mode ops? I could see them being necessary for HM or NiM, but story?