Posted 21 November 2012 - 04:47 PM
Sorry for the late response, but hopefully this post will help you or some other player. Jao is a tough battle, but the main issue is to stay alive for a long enough time to eventually kill him using something that can hurt him (such as poison).
Without using cheese tactics:
1. I'd advise you to be fully buffed upon switching zones, which is the only time that Jao would show up.
2. Immediately spread out your weaker characters, so that they won't be killed by Horrid Wilting, etc. Hopefully you have enough items and spells by now to keep them alive versus Jao's typical attacks.
3. Keep Jao busy using a tough fighter, such as Korgan or Minsc, who should have the Cloak of Mirroring. It is very important to keep Jao's spells away from the weak members of your party.
4. Kill the monk who is with him, who is relatively weak despite having some good abilities.
5. Eventually Jao runs out of spells. He then relies upon a relatively good melee attack. Still, it's nothing particularly bad if your best fighter is equipped properly. Slowly wear him down with the very few things that can reliably damage him.
Other general tips: Always get the Boots of Speed. If you have some other tactics-related mods installed, these might be necessary to keep your squishy characters protected. Always have the Staff of the Magi as soon as you can. Always have the Ring of Gaxx as soon as possible. If you have certain other mods installed that give you cool items that you probably shouldn't have, take advantage of those too. With all this going on, Jao should fall.