What do these Lvl 30's get out of it? False sense of accomplishing something?
As I am one of these level 30's, I will try to explain this:
The reason for this is the mixing of the existing equipment when the new patch came in. It turned out I now had some good equipment for level 18 (Legendary and Epic), but the equpiment for level 30 was non-existing. I even had rarley any useful parts for higher levels, only some Torsos, but no weapons. Unfortunately, many top-level players had more luck with their equipment, therefore I cannot play on higher levels unless I loose a thousand battles. So I bought some common stuff and upgraded it and together with the equipment I had, I now have a very useful level 18 build (I only loose if I get paired against level 22).
It appears success is partly due to the use of superior equipment and partly about developing a tactic how to play this build (one of the most interesting points in SM). The latter one is good, as good as it was in the past. The former one, however, is disturbing the gameplay, when only a few players are online and the rich and skilled veterans completely clear out their level range.