We need @scottg
I've never used any of the in-game characters for anything more than crafting. They are just "card-board" to me.
On the other hand as I mentioned in the XP post, there are advantages to using them and not having a party chock-full of your own characters.
About final battle strategy: Best practice in SOZ
Mob/Minnons first, "Boss" after (because he is melee-oriented).
Magic for the minion mobs (area effects), and
Fully enchanted bows AND arrows for your attackers (..with buffs for high attacks and added attacks), directed on the "boss". Make sure to use cold iron arrows or preferably adamantium arrows. Note that adamantium's added +2 damage does NOT take up one of the 3 enchantment slots. Both types of arrows can be purchased from sources in West Harbor AFTER you have taken care of their problems.
Note that just two well-crafted bow attackers with the proper enchantments and arrow-type can take-down the boss rather quickly.
If you do it right a decoy isn't needed.
Melee is an absolute waste at this final battle, and often get's in the way of a good strategy.
1st attack assuming poorly optimized spell-casting (..i.e. spell casters without spell penetration and high DC's to the large radius spells you need like Weird or Wail):
MKD from the Sorcerer or perhaps the Bard/Rogue with a scroll centered on tough caster opponents. Rogue is often the best choice here with a higher initiative assuming its UMD skill is high enough to cast the spell. It's also best to use a Rogue for this even if you have a caster capable of casting that spell from their "spellbook", instead that caster should be waiting 3 seconds for making their damage-casting attack. IF you have a Bard near them then also have the Bard use Curse Song (to lower saves) at the same time MKD is cast.
- wait half a round (3 seconds in-game) for your other characters and then use your area effect spells to "blanket" the entire "minion" area. Of course it was designed so that when doing this you'll have overlap on your toughest caster opponents (..i.e. they are standing in the middle). This provides that slight delay for MKD to work.
Usually hit them with as much power as possible.. Delayed Fireball Blast Empowered is always a good choice for one of the casters assuming Spell Resistance is lowered with MKD. Even with a reflex save a level 18 character firing this off should be able to do at least half of the damage necessary to kill any minion within the area effect. Horrid Wilting empowered is the alternative for a ASoCK.
Druids: Earthquake (..particularly if your foes have been cursed by your Bard). Clerics: Firestorm.
(..this is assuming non-Kaedrins.)
2nd: finish off all minions (including the "chanters") and slow the "boss" down with multiple grease castings (which have no save (to the slow effect) and no spell resistance). Consider casting Grease extended and always over-lap the area effects with a bit of offset to their radius's.
3rd: concentrate bow attacks on "boss".