Durendil: Second boss in Ulduar 25 to be solo’d. Not a hard fight, it just requires to learn to dps in BM (31K5 is needed to kill him). I used the spirit beast for the mastery buff, and macroed cower to buy myself a few seconds to maximize dps. It should also be possible in other specs.
It isn’t very long to find a eye/grip combo that allows you to last the full 8 minutes.