It would be great to have a separate mode which is exactly like Guard, but the dog will only attack creepers.
You'd be able to have a special role guard-dog ensuring you won't get blown up 😎

I've maxed the creeper-killing talent for the instant-kill, but due to there always being tons of other monsters my dog almost never gets to target a creeper in time. And sadly whenever they attack other mobs they get killed unless I help them.

Sorry my bad, didn't notice "Only Target Creeper" setting on Creeper Sweeper talent page