User blog comment:Zakzoor4/Sion-Rework must be made/@comment-18521310-20131027101517

Riot works on a risk-reward principle. Garen got a rework because it was low-effort, high-gain. It didn't take much to improve him and, since he's played so often, it would have a profound effect.

Sion is low on the list of VU champs for exactly the reason you said: he's not played much. Maybe a VU would solve that, maybe not. Either way, it's a lot of work for not necessarily much reward.