The best solution to zone instancing is to offer something better. First of all, more dungeons, the more it is, the better, less crowded. Second, sway the players interest in different directions(If there\'s nothing to do, other than kill kill kill, and the only places that offer that are dungeons, then I question the game itself. Third, make restrictions to enter some dungeons, (have permits to enter it), if it\'s related to a quest, there will be much less people, well at least less newbs.
If a game uses zone instancing, it\'s not a bad thing, but to me in my mind, I wonder how much thought they put into the role play of the game. Sure zone instancing was probably hard to accomplish, programming wise, but the 3 things I described above are much harder to accomplish as well.