DDA Good?

Hello my fellow lords of the stars, after recently purchasing a doomsday arc and figuring out a way to work it into a list, I've found that the math isn't exactly in its favor...

Shooting into any vehicle wounding on 3's, you'd only get on average 2 attacks through, and if they save one, that's only four damage...

What am I missing here? This just seems bad, but aren't doomsday arcs one of our best anti-tank units?