Make a proposal about all, then.
Seen from a basic point of view, something about a creature needs to get better when it upgrades, otherwise you'd not have any purpose in upgrading it anyway. Most get more health, but that's just not enough. To get somebody hooked on combat, there needs to be an achievement when you go to the next level. And if all creatures just hit single targets, you don't need half as many creatures as we have, just keep the one with the best stats and there we go, diversity is dead.
If not all creatures are single hits, we need multi hits. Multi goes for 2-4, so far so good, but with the drawback that it doesn't hit singles. Imo, that's a very valid concept that opens some nice options. But do you really want your best creeps to come with a drawback like that?
No, the best guys should do something a little more special than that. Out of all my fancy creatures, i get this extremely awesome option only with 2 basics, and with the drachorns. I'd almost dare to say that all is an extremely rare option, with only 3 out of 21 (based on my inventory, might be a few more overall) available families getting it, and those on the highest levels.
How do you remove all, but keep those selected few creatures a tad better than the rest, as they are intended?