Random damage would make the GCD rhythm differ each run though, so that would be a plus, assuming nothing else changes in the kits. I'd imagine a fight with a main boss on a timeline, and random events inserted in to cause complications. You can learn and practice these events, but sometimes a DPS will be chunked before a raidwide and the healers have to deal with that.

That said, this still leaves easier content out to dry, so eh.