Something you are still missing is the ability for the engine to have untargeted movement skills.
Unfortunately Grim Dawn looks ancient in this regard in respect to Diablo 2 and PoE.
I’d better not compare it to D3 at all, that took this to the next level by providing obstacle avoidance as well and you don’t get stuck as often happens in PoE.
A first step for you would be to at least try to implement the plain old D2 version of Whirlwind and/or a simpliefied PoE Whirling blades, and then try to work onward.
If you need a target try to fake it by adding an invisible monster on the mouse cursor and see if pathing can help.