It really depends on what you want to get out of the team in the end. If you want to run instances, get a tank class, a healer class and a dps. Warlock pets can only do so much before a real tank is needed in instances. It is so much easier filling 2dps spots than a tank,healer or both. For questing, forget healing, with a triple box setup nothing will get near you. Given that you are using RaF, I suggest pure questing, avoid the collection quests, and you will be 60 in no time at all, with very little down time regardless of what classes you choose.

I am always a strong proponent of triple mages, as I have run dual-, triple-, quad- and quint mage setups, simply for the sheer firepower in pvp and quests. Whether you spec them the same or differently will depend on your style of play and preference, but I always found the same spec (fire!!!!) was the easiest to manage. Their problem in any drawn out situation is survivability, assuming whatever you target can survive the sheer burst dps you can put out, and 3 x sheep and 3 x ice nova gives you a great deal of control over many situations.


Others here will tell you they enjoy the mixup of different classes; no-ones wrong, we're all here to have fun however we create our group. The best thing you can do is try something out for a level or two, and if the differences in spells / cast times between classes concerns you at all then that will tell you all you need to know.

Good luck with your decision