I feel you. I was excited for the sidearm too. Imho, it's just not good. The rate of fire is just too low for my liking. Even with a primary, it's not great. Also, that's how Destiny has always been. If you don't have a primary, you need to build around that, and it generally isn't as good if you just bring a primary instead. Special weapons generally do a lot more damage than primaries, with a few notable exceptions. That's part of the challenge with crafting a build. I agree the ammo economy isn't great and that it definitely needs improving, but if you're trying to run dual specials, you're asking for ammo issues, imho.