A little change to Singed's ult?

Okay, I have been thinking over this for a while, and I know his ultimate is awesome. But whenever I play a tank, armor and MR feel pretty worthless with so many . In fact, the only time I feel durable is with flat dmg reduction tanks like . So I was wondering, why not removing the bonus armor and MR, and instead granting Singed 30/45/60% dmg reduction during his ultimate instead? Numbers can change, but honestly, if the ultimate is supposted to make him more durable, it might as well do that instead of making us think it does that when it actually only takes their team 0.5 more seconds to blow you up.

NOSTALGIA REMINDER: It used to give you Disable Reduction. Good times...