It kinda depends on what kind of fights we are going to get, but fights where you need crowd control would benefit a lot from something simple as signs. It can be the same sigh with different colors, it can be different sizes or even numbers ... The system in WoW for example was really simple, but also really effective.

In WoW I always assigned, at the start of a raid, a certain icon/color to a certain player with crowd control (lets say a mage with sheep). So all I had to do was mark all the mobs without saying a word and everyone knew exactly what to do as soon as I pulled.

Some other people here got also great ideas, but it is really not needed. We do not need updating numbers or some kind of crazy system that we have to use while raiding to assign certain icons in a certain way. Let us just bind the icons/signs to a button and mark the mobs, it is really all that is needed. Easy to implement also.