Every Defender I've had I've had some minor issues with them but they offer the Best protection still.
I put it this way. The Defender is like a muscle car. It's clunky and noisy. However it is built for performance.
The ones I have after taking them apart a few times the inner plastic starts to creak a bit because the tabs expand slightly which causes it to have a little play in it. Again, like a muscle car it's built to perform, not the prettiest thing.
Mine has the bulge too.
A backup case I have but don't use is the Caseology Leigon. It's their Defenderish case and it's pretty darn good and comfy in the hand. It doesn't quit have the protection the Defender has, but it's similar to the Commuter and Unicorn Beetle protection wise. A good buy if you don't want to spend $$ for Otterbox but still get good drop protection.