Scorpikors look very impressive. Are you planning to give them a super-upgrade (like with the Nightmares)?
But if we are going to add a third upgrade, then it would be worth introducing something alternative for Tier 6, so it would look like this:

With this format, we could bring back Hydras, but honestly, I don't really want to see Hydras in the Dungeon... After all, they are creatures of "Tatalia/Swamp/Fortress".