Riot Shield Nerfed?

I've loved using the riot shield on mw3, and today I took it out after not using it for a while and found I was dying insanely easily... I used to always go positive with it, but now I'm dying loads - people shooting directly at me are killing me :S Also I'm pretty sure I used to be able to work out where enemies where and such even when they were shooting at me, but no longer... Now my shield is just a mass of sparks and they can run loops round me. So, has it been nerfed? Other riot shield users noticing a difference? Or am I just having a bad night o_O