[GAMEPLAY] Miss Fortune BUG (Or stealth fix?)

Before 5.1, when MF got a Bloodthirster, the shield it built (or any shield on her for that matter) would prevent her passive from being disabled so long as her actual health bar took no damage. Now it seems that, even with a shield on, her passive gets disabled on any incoming damage or ability.

Is this a bug, or is this now the intended behavior?

It was nice to have the shield when around minions, because even if they were attacking you, so long as you weren't taking too much damage (from like, a champion or whatever) you could keep your passive up. It made Bloodthirster a much more worthwhile item on her, and paired her off nicely with supports who could shield her. I'd be sad if this is a permanent change. =(