Our gasblocks don't leak. The ones that went through the military trials never leaked at all. All in the design.
When you dimple a barrel, you change the local stress state which can lead to accuracy issues and some irregular heat flow. Inspection of barrel interiors, especially chrome lined, has revealled that in some cases, the first point of failure and cracking of the chrome lining occurs at the point of the exterior dimpling. More often, it is at the gas port though.