Is there a difficulty issue there though? In order to make it possible to actually *WIN* a fight against 3 baddies fighting you with those tactics, any single one of them would have to be fairly easy to take down, making 1 on 1 encounters last 3 seconds. If not, you would simply never win if you encountered 3+ enemies in a group (or at the very least, the battle would be epic in length as you grappled with the melee guy, always turning and dodging in order to avoid flanking while trying to out maneouver ranged spells).
If attacks were deadlier, making it possible to kill enemies in a few hits, instead of the usual damage sponges, you'd have to zero in on the weaker ranged guys first, not go for their "tank". Stealth players would also benefit from being able to take the squishies out before engaging the others (if at all)