I get why filtering the RMT is difficult, but honestly, the fact that you're not doing much is scary. Here's some simple ideas.

Don't allow people under level 50 to shout more than twice a minute in town, and four times a minute outside of town (shouldn't infringe on ability to ask for raise).

Don't allow people under level 30 to send tells to more than 6 different people in a minute.

Create a type of reporting that that when 50 or more people report someone for "chatlog abuse" around the same time, it mutes them until a gm investigates. Make abuse of this a punishable offense.

It's stupid, you can't even ask a question in shout because people ignore it because RMT own it.