Neon isn't generally overpowered, but at the highest level neon is so much more annoying to play than prime chamber. If I was playing pro, I would rather play against prime chamber than a really good neon player.
Riot is really good at creating agent horrible to play against, not really that fun to play, and with low interaction with mates and that can be both weak and frustrating to play against, while beta agent are probably the best agent for the sanity of the game