Grindal: The pull of the rift

I was daydreaming, and i realized that there really isnt a mage that scales off of hp. Of course, theres tanky mages like brand, ryze, maybe even vel, but i want to create ( or concept) a specific tank mage who scales off of armor/resistances/hp who still has enough cc to be viable.

Grindal is a tank mage ( ranged) who is primarily played toplane, and can set up engages and disengages for his team. While he has some damage, he is far more effective in fights.

Passive: Obstruct If Grindal has 60% percent hp OR mp, he will have a small slowing field around him that slows enemies who try to get pass him by 20% of their max movement speed. Grindal also gets more tenacity ( capping at 40%) the more hp he builds, with every 1000 hp granting 10% extra tenacity. However, building tenacity on Grindal is half as effective. Grindal gets bonus AP the more tenacity he gets ( 50 p for every 10% tenacity)

Q: Gravity Blow ( scales off HP and AP) Grindal is slowed by 20% of his max movement speed for .75 seconds as his next auto attack charges up. His next auto attack will then knock back his enemy a medium distance. After this knockback, Grindal then temporarily gets 20% of his maximum movement for .75 seconds. If the enemy champion collides with a wall, the enemy then becomes heavily slowed for 2 seconds, while being silenced for 1 second. If the enemy champion is knocked back into Gravity Field (e), Gravity field's root then immediately activates.

W: Gravity Vector ( the speed slightly scales off of armor and magic resistance) When activated, Grindal can place down a gravity zone on the floor. If running in the direction of the field, both allies and enemies get a movement speed buff for 3 seconds (but allies get more movement speed the more this skill is leveled up). When running against the direction of the field, both allies and enemies are slowed for 2 seconds (but enemies get a bigger slow the more this skill is leveled up). However, If an enemy is slowed by one of Grindal's abilities, then they will not be able to cross against Gravity Vector's zone.

E: Gravity Field ( scales off of tenacity, Hp, and Ap) Grindal places a small slowing Gravity field on the floor. The Field slows all units for as long as they are in there, heavily slowing all enemies by 70% of their maximum movement speed, and slowing allies by 40% of their maximum movement speed. After 3 seconds, the floor then collapses, rooting all enemies still in the zone for 2 seconds.

R: The Pull of the Rift ( scales off tenacity, Hp, Ap, Armor, and magic resistance) Grindal readies himself for 1 second, then begins to suck all enemy units in a large cone area in front of him and to enemy units impacted by Obstruct directly in front of him. This Pull slows all enemies who tries to run in the opposite direction of the pull, but speeds up enemies who run in the direction of the pull. This pull lasts for 4 seconds, and does a tick of damage every second, with the damage increasing for every unit sucked in ( with a bigger damage tick per second the more allies caught by the pull). During this time, Grindal takes reduced damage, with the damage reduction increasing to up to 70%, depending on how many champions were caught. This pull cannot pull enemy champions/minions through walls, but the pull will still effect them ( meaning if Grindal hypothetically ulted from red buff to the krugs, the krugs would be pulled, but would stop at the wall).

Of course, there might be a few people who think that people can then just run past grindal during his ult. However, if Grindal has over 60% of his mana or hp, then Obstruct will occur, slowing enemies who try to run past him.

So this was my concept of a gravity themed tank mage. Viable? Problems? Would love to see or not? write it and ill keep the replies in mind as I think of more concepts. thx for reading my daydream thoughts :D