@Peri_Longbow_plz As someone who spends a lot of time with their knockdown shield and being rezzed by teammates, I rarely see what you're describing. Are you pinging the enemy that is thirsting you?
As long as you're reasonably close to your team, the knockdown shields keep you alive enough to be rezzed or even to shield your teammates. Of course, you should ideally have some cover and know how to turn.
If you're talking about surviving 3 players all going against your shield, that's obviously not going to happen and it shouldn't. Also, if you're isolated away from your team or wide out in the open, it's pretty much to be expected you'll be killed. In fact, you can easily have a finisher performed on you, which ignores knockdown shields anyway.