One of the biggest issues in terms of "gassing" is the load used.
A gas system can be tailored to NATO spec ammo...the powder burn rates, gas volume available at the gas port at a specific rate of fire, velocities at certain points in the barrel and at transition to the muzzle device, etc...are known or can fairly readily determined with the spec ammo. But very few shooters are using 100% spec ammo 100% of the time (and even then there is some variation within accepted performance specs and whether or not one necessarily believes what's printed on the end of the cartridge box). The gas system can actually be tailored for any load once that load's properties and performance are known. Unfortunately, a rifle manufacturer can't tell its end-users that they can only shoot one load amongst hundreds that are commercially available some or part of the time. The same gas system that might be great for one load may be over gassed with a different load and under gassed with a third load. Even a particular load from the same manufacturer will differ from batch to batch (or in some cases, round to round within the same box or ammo)...it won't necessarily be a huge difference, but it can be enough to impact performance.
The answer, if a problem exists at all, is going to vary with the circumstances...gas port diameters, action springs, buffers, adjustable gas devices, carrier weights, expansion chambers, pig tail style gas tubes....no one answer is perfect for every build and every load.
Steve/RRA