None of the 4 I've owned needed one to function correctly. If I wasn't running a suppressor, I still wouldn't have an AGB. As it stands, more than 3k rounds mixed suppressed and unsuppressed (without cleaning) before the first hiccup convinced me that the gas block is the least significant component to gas issues.
Gas port size, recoil spring/buffer combination, and gas tube length are the primary drivers of a functional DI system, by my experience anyways.