Why is Thresh still having naturally low cooldowns/mana costs?

I fail to understand this, {{champion:40}}, {{champion:43}}, {{champion:267}}'s mana cost and cooldowns are rediculous compared to {{champion:412}}. Does Riot just want every support to just play him all the time. He does more damage then all three of them and gains natural armor better then {{champion:44}} does and completely makes him useless. Why did Riot design this thing and put him in the game when he outclasses every other support?
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