I don't think that just increased visibility will help much here. There are still way too many pending synonyms, and not all can be voted on by any given user. If that can be fixed, then increased visibility would be a big plus.
A filter that lets you see the ones you can vote on could help improve this page a lot. A review queue might be overkill, but it would effectively accomplish the same thing.
One way to go about this is to have periodic synonyming parties where users gather in a chatroom and discuss/vote upon synonyms. Over here, if the vote is falling short due to lack of users with activity in the tag, you can have a couple of mods using the synonym tool if there is enough consensus from the broader community in the chatroom.
Alternatively, relax the requirements to be able to vote on a synonym.