One-profession label

If you want to have a one-professian-build, you simply put attribute points into your (logically) primary profession. I have an all ranger build, a pure ranger. I would like to have a possibility to label myself as a pure ranger. My second profession was mesmer, now it is monk. I do nothing with this second profession. Yet I am labelled as R/Mo. This can be confusing; it looks as my character is something, it isn't. Good idea?

no. It's fine. labelling causes opposition to think you might have something you don't (smiting/healing/prot.)

In PvP and Arena you should have no label at all. First profession you know from the armour/dress. Second profession? you have to find out. Know your enemies, that's combat-experience; it should pay-off.
But I have not played PvP and Arena. I was referring to finding and selecting party-members for coöp-missions.

I don't know why you wouldn't want to have a second class anyway. They might add something really cool in the future, plus it expands opportunities for your character. I'd like to see a labeling system where depending on what two classes your character is, you get one name. For example, a Warrior/Monk could be labeled as a Paladin.