lol i don't even know how to even begin this, i just played it on PBE and it's a pile of dog shit lol
first of all nobody got time to stack passive in a team fight and expect a blockable skillshot to stun anyone
second he's lack of consistent damage will outweigh his E heal and you'll be forced to activate shield and waste your heal
third he has no mobility whatsoever no gap closer no escape and a 95% goddamn 95% slow when devouring enemy champ for 2 seconds while he remains untargetable in your belly, you can't carry your enemy under your turret, you can't attack him and what usually happens after you spit him out is an unworthy trade since you're an ap champ and you're just outta offensive abilities. and then shield keeps you from dying and then you found yourself outta mana and have to go back home or wait for the enemy champ tower dive your ass before your shield comes back...oh wait...you only get a shield when you take more damage...well i guess you're screwed
as for supporting, you can protect you adc by eating him...every 16 seconds! wtf! and yes you can carry your adc away from danger but guess what? the 30% move speed is only applied when you're RUNNING TOWARDS THE ENEMY. so here's what usually happens at bot lane, you Q, they're slowed, you walk up to auto, you get chunked down, you get three stacks, you eat adc, you use shield because you're so low at this point that support can kill you, your shield grants full health and both you and your adc attack enemy support, but then you spit enemy adc out, your temporary shield goes down, you get killed by enemy adc with one shot, enemy adc is probably half health since you did chunked 20% of his health down but now it's a 2v1 and any support with a protecting mechanism can help enemy adc get a double kill.
he might be able to work as a jungler, eat monsters, spit out with aoe damage, gank every 180 seconds after lvl 6, and try to stack up passive since it's the only way for your offensive abilities to become a cc.
good luck with this riot failure.