Coming from totally new player to fRO but still:
How about implement them, get people to PvP with them and then check the results after a week or so (finding out which classes seem to be best) and perhaps ask for opinions about them from about 20-30 people who are chosen for that job. That way atleast the problem areas could be pinpointed.
Ofc, I have not enough info on the third classes and their skills/potential, so if I'm posting age-old idea/info here, just ignore it :)