'm betting he'll stop Wanda as soon as he realises that she's about to aggro on Jillian, if he can, and thats what the next strip will involve.
I believe the opposite- Parson will see that battle has already been joined, and immediately order all available archers in the hex to help his caster.

Compare RTS games where someone attacks too early. They made a tactical mistake, but refusing to back them at that point is a bigger tactical mistake. I'm guessing this battle will end with some wounds, some lower-level units killed, and an unresolved rivalry between Wanda and Jillian.