if anyone plays, no one will pick the Defender, as he's not even worth his price (2800).
But the Wild Ent is quite decent.
If you compare the Guardian, -5 damage, -1 speed, -6 initiative, who would choose him with such competition?
The Wild Ent with its 15 defense will fall very quickly, and again, the stack is dangerous for the Subjugated (if they are taken, you will regret taking them).
Guardians can hold the defense firmly, even in vanilla, you often have to break the Ents' defense to get rid of them, and these have immunity and 35 defense + they retaliate to all attacks. They will be the wall that won't let enemies through to the archers and druids; of course, it is very important to have a tactic to position them correctly.
In any case, this is not final, and only practice will show the true state of affairs. Based on feedback, it will always be possible to adjust the overpowered (or weak) unit. I'm only playing with my brother via Radmin, which isn't enough to assess the changes.