Aren’t you able to rebind it in the Keybind menu? I played on controller for quite a while far before the Controller integration in 8.0.5, using JoyToKey (MoP=>WoD) then Steam Big Picture (WoD=>SL).
I had: RT = Shift, LT = Ctrl, LB = Alt, Key = A, B, X, Y, RB, Select, Start, ↑, ↓, →, ←
So i had those combos:
Default Key, LT-Key, RT-Key, LB-Key, LT-RT-Key, LB-LT-Key, LB-RT-Key
So i had technically 77 binds, not all used for rotations, since some combos dont feel natural to do, and in some case there was actions like jumping that was on Default A as a natural convention for Western games to have.
If Blizz does not give you the option of having more than two multipliers, Steam allows it with ease, through Keyboard key emulation.
It’s the only real problem i had. And still, with a Steam Controller, i’ve been able to heal in Mythic Nyalotha on my MW monk. But conventional controllers have this limitation. Dungeon healing is easy, tho. I targeted my mates by using ↑↓←→ and me by just tab-targeting the mobs so i auto-targeted myself when using heal.