Party AI can be 'good enough', though, in some circumstances. If you can command the party as a whole to attack a specific target, and then fine tune commands as required, then a real-time-with-pause type system can work fine. Melee warriors do not need a lot of babysitting if there are reasonable options or presets for target selection, etc, once their initial target is defeated. Archers can be a problem if they attack distant opponents and draw them into the fight, but that can be mitigated by how you approach a target, and the position you attack from. As long as there is only one mage in a party, you can select that character to control directly (I don't think I've played a game yet that had a good AI for magic use, or anywhere near the customization options to configure a reasonable behavior in most situations).
For larger parties (about 5 or more) or multiple mages / archers, I would prefer a turn based system. With predominantly melee parties, it is not that hard to implement an adequate AI.
