1.Exit game
2.Enter your WoW folder, delete the cache folder
3.Enter your interface folder--->addons and delete every file that starts with Blizzard (these will be recreated)
4.Enter the game, make sure you have Projected Textures enabled, and set your particle density to high
5.Press esc, enter the interface menu--->display. Once there, uncheck Emphasize My Spell effect.
6.Log out, and then back in.
This worked for me and all my guildmates when we were in RS, and Halion can be quite hard without seeing the textures on the ground-.-.
There is certainly easier ways to do this as the others above me already mentioned, but this worked for me like a charm. GL