There are RMT guilds full of lvl 50's behind these spammers.
These RMT guilds use the hacked accounts as proxies, for trading and spamming.

Get to their core; find the RMT guilds by looking at gill transfers and what not, look for RMT activity and back trace.
Remove the RMT guilds and all their lvl50 RMTrs, remove the core, the spammers will go as well. Get rid of these lowlifes.

It's 2013. Put some effort into it.