Maokai's New W (concept)

Hi Summoners and Rioters! I thought of a great idea that could put Maokai in a better place as people believe he didn't get majorly reworked like Sejuani and Zac for this year's tank update. All his moves are great EXCEPT his W is odd in my opinion. Why would he have two root moves now? Sure one applies to multiple targets but in addition the W makes you untargetable for a few seconds. But the W seems useless now that there is the new ultimate. As such, I have thought of a new W ability that should take Twisted Advance's place.

W - Vengeful Maelstrom: Maokai shields his allies by drawing power from hostile spells and attacks, reducing non-tower damage done to allied champions in the area. When Maokai ends the effect, he unleashes the absorbed energy to deal damage to enemies within the vortex. Toggle: Maokai surrounds himself with a magical vortex that protects him and allied champions by reducing damage from non-turret sources by 20% for up to 10 seconds.Maokai can end the effect to release the stored energy, dealing 100/150/200 (+50% Ability Power) (+2 per damage absorbed) magic damage to enemies within the vortex. Maokai can store up to 100/150/200 bonus damage.

Now I know what you're thinking- that was his old ultimate. But bear with me this ability can be toned down.

Let me know your thoughts with Maokai having two root abilities.