Watching some streams he looks okay. He has high burst on a single target with decent long cooldowns even with CDR on his Devour and spitting targets out seems to have a large AoE which I believe could be more of a problem than a single target nuke. I do like how the skill has offensive or utility for the team though, so you could potentially save an ally through all the burst or take a enemy out of the fight.
His Q is also single target and a skillshot that can be body blocked on a low cooldown, so it seems okay to me.
His shield is the thing that seems absurd to me considering you build HP on him so basically you can have around a 8k-9k hp late game on average if you time your shield correctly (4kish on average if you build HP items) but I do understand the need for him to be tanky considering his lack of reliable AoE, movement speed, needs three autos on a single target to maximize his potential(which if you build HP you attack slow, and move slow which makes it difficult in team fights), and single target damage although I feel with this shield being so strong it either forces you to focus him and burn through the shield+base HP allowing his team to be more effective or let him run rampant and devour targets without contest which then his W becomes a problem.
His ult seems fine to me it has a mediumt ish range considering global ults... the lack of vision/channel time allows for some outplay if you think quick, but the damage based on HP is a little too strong in my opinion considering his ultimate active already has a great function...could use less base damage in my opinion.
Gonna give him a try this week to re-evaluate but as all newly released champions they usually have something OP or broken in their kit which is why the PTR is there for people to give it a go. And if you build him AP I believe it's a waste considering you can get bursted down in seconds even with your shield your short ranged abilities and need for auto attacking which is highly unlikely in a team fight unless you build an AS item and even if you do you will most likely only trade your life for your targets since you most likely have to burn flash to even get in range of your enemy since his Q (slow) is single target which can be blocked by allies (tanks) and minions which to be honest will be quite hard in a team fight with all the chaos running around. Group fight wise that is. 1v1 he is definitely strong maybe too strong but this isn't a 1v1 game.
Let Riot run it's course and wait for an official release before busting out the pitchforks folks.