This is a low priority bug, but it might be worth looking into because the way that deploying a second boost champ works is a little visually ugly in itself. I had a Goblin King out boosting my Goblin Cropsick up to just under 75 hitpoints (which is the number he explodes at due to IEI). I deploy a second Goblin King with Boost:goblin. The second boost doesn't actually stack, but it seems to apply to all the goblins momentarily as they all get +5 hitpoints (+10) and then it immediately goes back down to the previous +5. Needless to say my Cropsick exploded.