User blog comment:James12708/What we know about the Reapers and what I thought would happen in Mass Effect 3/@comment-24174486-20120814200132/@comment-4950455-20120814202321

Sovereign went down very quickly once its barriers dropped. Admittedly, it wasn't shooting back, but I really wouldn't underestimate how much of an advantage that would be.

On the other hand, Reapers aren't indestructible as it is - you're personally responsible for the destruction of three or four destroyers, the turians killed several at Palaven, etc. According to the description for Azimir, even the batarians managed to take out a few destroyers, and we know the Hegemony went down like a house of cards. So it's clearly more the damage they can do then the damage they can take which is the issue.