Blackmore should have been a really intense (in a good way) fight if only for how claustrophobic it was, but the second half was really too much. I've beaten him, obviously, but I'm still convinced that certain combinations of his attacks are impossible to avoid. (Unrelated: Firefox doesn't think "combinations" is a word? WTF?) Eligor wasn't necessarily unreasonable, but bringing him down required you to work at a very slow, deliberate pace to avoid excessive damage, and it was really punishing to spend ten or fifteen minutes chipping away at his health only to die at the last second due to some careless mistake.
It's really those two fights that disrupt the otherwise awesome Boss Rush mode. Because really, the majority of Order's bosses are spectacular.
You exist because we allow it. And you will end because we demand it.