Actually, I considered moving griffons to tier 6 (Iris would be thrilled), but I reminded myself that paladins are not just knights, but practically the hand of Elrath, although griffons are likely not inferior in strength. Besides, the order will remain without flying creatures until tier 6.

Added 9 minutes later
I would like to return to the topic of hydras. If they are moved to tier 6, I suggest somehow changing the concept of upgrades. It would be good to make a fundamental difference between the upgrades, for example, one upgrade would remain a sturdy tank (you could even give them the "taunt" ability), and the alternative upgrade would be focused on dealing damage.