I posted something like this early in WoD too with shadowmourne but there was a hotfix that addressed the issue... however only at level 100.
At level 90 to 99 you can do skirmish arena with Tier 2, AQ trinkets, Shadowmourne, Deathbringer's Will. You name it. Every trinket, every setbonus, every procc weapon. Everything is viable, it all gets scaled up. Play with whatever you enjoy.
If you don't believe me enter a skirmish on that level range and check the stats on a lowlevel item.
Gonna have some fun with my shadowmourne+deathbringer's will warrior, see you in skirmish!