In FFXIV we have been giving a wonderful system for marking enemies with symbols. Unfortunately it is incredibly restricted and useless outside of leves. Some things that I feel would make this system an integral part of combat:
1. Make it usable outside of leves. This one is a no brainer, why was this ever restricted to leves? There are many situations outside of leves (NMs with groups for one) where this would be useful.
2. Remove a mark only if the same person attempts to apply it twice. I've been in quite a few situations where the mark has been removed by separate people trying to mark the same target. This can lead to a bit of confusion or at the very least taking extra time to re-apply it.
3. Give us a macro command for targeting specific marks. This would help increase their effectiveness in battle. When their is a group of monsters, especially when they converge on a single target, it can be difficult to pick a specific one out of the group.
4. Add a more diverse choice of marks. A few more marks for things like bind, sleep, no WS, kill order, etc... would be helpful. Yes the group could specify that Diamond means sleep, Spade means no WS, Heart means secondary target but they're not universal symbols and can vary from group to group causing some unnecessary confusion.
All in all I believe the marking system is fantastic, it is just restricted to a point of being useless in most situations. With dungeons coming up soon we could really use this marking system.