Tactics for the Swamp (Fortress).

Just make them stronger or/and move them to a higher tier...

And who would replace them?

I mean, after a serious battle near the Swamp, only Gorgons, Hydras, and Basilisks survive. => The rest aren't very good at defense. And they shouldn't be used to hold back the enemy. But on the other hand, they can deal decent damage, with the support of stronger creatures.