Make Tahm less of a Guardian angel and more of what he was supposed to be

Tahm's brutal atm.

Lane phase he spams Devour (10 second cooldown), making it mission impossible for the enemy to poke or chunk the opposing adc.

Tahm is ment to be an initiation support, a playmaker for more mid - late game, he is supposed to eat allies with good initiation (Malphite, Amumu, etc) run at enemy bunches with that movement speed steroid, spit the ally out for him to charge in, and grey health to stay alive.

What I think Tahm needs is more complexity and to be more rewarding if he gets his passive stacked on an enemy. I think Devour should have a 30 second cooldown if he eats an ally. But, if Tahm were to get his passive stacked on an enemy and spat him out, the cooldown is 10 seconds, like it is right now. Also if Tahm were to eat an ally before, and it was on the 30 sec CD, and he were to get his passive stacked on an enemy, the cooldown would be erased and he would be able to eat the enemy.

Or is there an other way to make Tahm less of a guardian angel?