Just tested this and it happens for me too. It's actually a long time issue, but I guess people just stopped using skills with two names and we never went back to fix the issue.
The underlying problem is that our spell manager and current cast system are setup to work with only one name per spell, since we use spell names. It looks through the list of available spells and returns the first one on the skill bar. as the only other way to differentiate spells is to use their spell id. At one time (Jan of this year), we had a system where you could use Arc, Arc 2, Arc 3, but that was removed because it was part of a spell caching system that was causing crashes and other instability due to the memory model used in this game.
I just re-added the number system as a temporary fix, so you can use the number to get support for more than one name. The actual number you use is dependent on your character though. So for example, you'd make the following changes to Exile.cs after the Beta was deployed:
Inside function RegisterTotems: RegisterTotem("Arc 1"); or RegisterTotem("Arc 2"); instead of RegisterTotem("Arc");
Inside function RegisterMainAbilities, the other number not used in RegisterTotems: Register("Arc 2"); or Register("Arc 1"); instead of Register("Arc");
You should be able to do this for any skill name as well, but you'll have to work out which skill is which, and then update Exile accordingly. If you change skill gem placement or order, it might be possible for the numbers to get swapped, as the order is determined by the server. A new beta can't be deployed right now because of the next set of large core changes being integrated (possibly late this weekend), but the next beta will contain the shot term fix.
