Auto resolve invariably wastes mana when a channeler is in your army.

Expending 2 or 3 mana on every encounter consisting of  a single spider or wolf  is ridiculous when you're traveling with archers and heavy cavalry.

Right now you have 2 options:  Tactical and Auto-Resolve.

I suggest having 3: Tactical,  Auto-Resolve,  Auto-Resolve (melee)

The latter would let your archers and infantry deal with the issue while your casters (and monsters with special abilities!) do not burn precious mana on "trash mobs".

Alternatively: checkboxes below the Auto-Resolve button.

X  use unit special abilities (stone giants, dragons...)

X channelers cast spells.

X channelers avoid melee - Fireballs, earthquakes, throw the kitchen sink. (not sure if "special effect units" should do that, too?)

This way you could decide which cases of auto resolve would warrent which level of... artillery. A stone giants AOE attack can really tip the odds and they don't need that much time to regen their mana.