I dont particularly run M+ past a 16 (theres no actual point other than ranks) and for the majority of bosses with Tyrannical 1 charge of HRW tends to be enough, especially since generally engage bossess with 5-6 runes and 90-100RP at the ready.
and for anything below a 10+ i generally dont even take HRW as ERW is enough for the 30-40 second boss fights and just run Bracer/helm (i run Ice cap for sub 10s).
I would say legs + belt for M+, you can always pop on the ring in exchange for legs before a boss anyways