Especially in the first part of the game, I lose heroes too often on auto combat, forcing me to battle manually even if the odds are very good.
The SP waste before I have enough essence is just as annoying.
I also think it should be kept simple.
Make it too complicated and you'll have to change settings before each combat, which will kind of miss the point.
I'm thinking of something along the lines of setting priority of 3 orders: magic, weapon, hold.
magic first means blast until you're out of essence.
If it reaches weapon, it will either charge or fire, depending on the weapon type.
Hold means avoid walking, attacking only if someone is on range.
For example: your hero has magic and is armed with a sword.
Set the priorities to: hold, weapon, magic
translates to "do not charge, blast with magic until someone comes close to you and then use the sword"
Set priorities to: magic, weapon, hold
translates to "blast with magic until you're out of essence, then charge using the sword"