I'm sure SE can easily add filter to /tells but you have to ask your self...

Whats better?...Getting /tells from RMT....VS... getting /S /Shout /Yell from RMT?

The very moment SE restricts/filter the /tell chat, RMT will reprogram there bots to use the /S /Shout /Yell chats. and because of the range restrictions of this chats, you will than see REAL spam on the chat logs not just 1 tell from a single RMT bot.

If you look at your /tell log carefully, you might notice that you only got ONE or two RMT /tells from the same bot. This is because the odds are that RMT send mass /tells to everyone once or twice than a couple of minutes later they proceed to DELETE there character and make a NEW one thus bypassing the Blacklist filter.

this means that SE has to implement a character deletion/creation restriction just to combat RMT. T_T

*** When this game came out I was playing TERA and decided to give it a try as NEW player. the first thing new players are introduce to is RMT harassment non-stop. this became very irritating to me and I ragequit after lvl. 4. as I founded it unacceptable for a P2p game and still deciding to continue trying the game or go back to TERA. I went back to TERA. than it became F2P so came back to FF14 couple of month after Tera was f2p..

***I don't think there is a real automated solution but SE could do a bit more to slow them down. i.e lvl 10+ restriction ect. and GM monitoring of "ALL" severs which is not cost effective. go in as new character...right click/banned any RMT spam it receives...again this is just too much to monitor in all servers unless is automated.