That's why I said one big group instead of several small ones. If you enter combat each time and have to destroy 4 Rats again and again it's boring.
But if instead of fighting 4x 4 rats in boring fights, you could face one fight with 16 rats instead. They surround you, no safe spot for your mage anymore, more attacks per turn than your warriors can block each turn and so on. It becomes a fight for survival. But you can maybe use AOEs instead of just single target damage, which would also make this fight resolve faster than 4 single fights. The feeling of being more powerful compared to a rat would still be there.
I think I'd still rather face 16 rats in real time.