I tried the Mythical Stormheart as a Pyromancer and as a Sentinel
I prefer the Sentinel because it has more mobility and also it easier to proc the 3 proc from the devotion.
I did SR 80 but the speed wasn’t that great. It would be really nice to have Righteous Fervor damage added to the Mythical Stormheart.
What i have tried : Sentinel, Level 100 (GD 1.2.1.2) - Grim Dawn Build Calculator