For a tank, Maokai deals quite a lot of damage
Kinda too much for a tank to be able to deal given his stickiness, 2 forms of hard CC, a ranged 2 slow combo (E slows on impact and detonation), damage reduction, and heal.
He should have all that utility in his kit, but should also not be able to out damage half the team in the process when building an entirely full tank build. That is not right.