The better solution perhaps is that Rams should just not auto-attack anything that they have a 0.01 attack multiplier against?
As far as fleets not auto-attacking "nearly indestructable" things, it'd be nice if instead of just ignoring them, they just de-prioritized them. So if there's softer targets available they would hit those first, but when there's nothing else to shoot at, they might as well take their shots (presuming they're capable of doing actual damage to that target).