Yea if you see someone with a shield immediately bash them. These people usually don't know this and they will be backing up.
I run an assault shield/crossbow class for SnD, which is pretty much the class that destroys the class I use. Semtex and crossbow sticks to the shield whether you are wearing flak or not kills you so remember that.
Are you in Hardcore? I play Core and when I get stuck by a bow on my shield I always survive. However getting stuck by the sticky is a kill. If you get stuck by a sticky nade and try to plant your shield this glitch happens where it instantly explodes killing you.