The only counter to gunner is AT, which is also overpowered in this ver but not as much imo
Gunner is too op because it was a new class, it wasn't "intended" by the developers as they nerfed/balanced gunner in following patches... Unless they wanted to make people try a new class before they nerf it, which also doesn't make any sense on EuroAion when the server had already started from 4.6
People don't care for "unchanged" Aion, it's already filled with cosmetics from future versions, some new events etc. It really wouldn't hurt tweaking gunner stats a tiny bit and observe.