Nautilus - W Changes

As of now Nautilus's W reads like this on the LoL Wiki:

ACTIVE: Nautilus gains a shield that absorbs a certain amount of damage. The shield dissipates after 10 seconds if not already destroyed. While the shield persists, Nautilus's basic attacks are enhanced to debuff all enemies within 175 range of his target, dealing bonus magic damage over 2 seconds. Titan's Wrath also resets Nautilus' basic attack timer when first used.

It scales like this:

SHIELD STRENGTH: 100 / 150 / 200 / 250 / 300 (+ 10% bonus health)
MAGIC DAMAGE: 40 / 55 / 70 / 85 / 100 (+ 40% AP)

Basically, Nautilus get's a shield which scales with max health.  Then, while it's up, his auto attacks to apply a DoT.  

The problem with this mechanic is that as a tank, Nautilus soaks damage.  But a grand majority of the damage he can put out is through his W.  Meaning that in order to do his job as a tank, he fails in his job to do any kind of damage (which most tanks need to do at least SOME of).

So, I propose a change to W.  Make it last only 5-7 seconds, but keep the damage during the entire baseline duration.
In other words, make it more like Lulu's Help, Pix!, where Pix still does damage on AAs even if the shield is broken.  It should read something like this:

ACTIVE: Nautilus gains a shield that absorbs a certain amount of damage. The shield dissipates after 5 seconds if not already destroyed. For five seconds, Nautilus's basic attacks are enhanced to debuff all enemies within 175 range of his target, dealing bonus magic damage over 2 seconds. Titan's Wrath also resets Nautilus' basic attack timer when first used.

This change will make it so that Nautilus does not have insane uptime on his W damage in fights, but he also won't have insanely low uptime on it either.