@Meddler/Repertoir/etc. - Your thoughts on a "steal offensive stats" ultimate

In my continued work on trying to make a thief Champion, I've settled on the following ultimate (excerpted from the above link).

Severa blinks to target enemy Champion (400 range) and drains 20/30/40% of the target's attack damage and ability power for 6 seconds. Severa can activate The Big Heist again within 4 seconds to transfer the stolen stats to a target allied Champion for 6 seconds. If she does not reactivate it within 4 seconds, she automatically transfers the stolen stats to herself.

All stat modifiers decay over their respective durations. Enemy Champions affected by The Big Heist are considered Easy Prey for the duration.

Got an out-of-control Xin Zhao with a Rageblade/Devourer combo? Hit him with this and all that power of his turns against him (for a limited time). To make it even sweeter, you can then transfer those stolen stats to your team's biggest damage threat, turning them into a nightmare for the enemy. Be warned, the effects don't last long!

Considering Trundle already can jack a large amount of tank stats from more durable opponents and make himself almost invincible sometimes, what would you say about an ultimate that jacks a large amount of an enemy damage-dealer's damage power?