Well, here's my preferences:
My Warrior's Best party:
Paladins
Knights
Inquisitors
Archmagi
Demonologists
Reserve:
Any lvl 5 unit with over 700 health for sacrificing to replenish the demonologists or other troops I may need, except Black Dragons
Druids
Why?
Paladins + Knights are a wicked combo. Both are perfect tanks and are very hard to kill. Using Archmagi's ability Magic Shield will reduce the losses during the battle and will make the resurrecting a lot more easier. Inquisitors provide extra resurrecting and the Demonologists provide very powerful scapegoat units for the AI to prey on. The druids are both summoners and rage hoarders - their 9-cell attack may not be worth much damage, but provides a significant amount of rage. As for the lvl 5 unit, anything over 700 HP will do, because I can easily use lvl 1 sacrifice on it.
My Paladin's best army:
Paladins
Knights
Archmagi
Inquisitors
Priests
Reserve:
Demonologists
Druids
The Paladin has a medal that improves the damage of all paladins, inquisitors and priests by up to 40%. You should be aware that this is simply wondrous. As such, I consider those 3 units mandatory. While striving for this army, I usually take the resurrection skill ASAP and push it up to lvl 3 as soon as possible. With this army and resurrection lvl 3, I do not care about losses. The AI usually goes for the priests, and I don't mind at all if they die, as long as the only thing I'm losing is them. Archmagi, Demonologists, Druids same as the above.
My Mage's Perfect party:
Well, as a mage, you need to be flexible. My current mage on impossible is lvl 22, 80 battles, no losses so far. I had to use the thieving tactic to get all the way to Reha. I managed
Paladins
Knights
Archmagi
Chosha's
Tirexes
Reserve:
Inquisitors
Gorguanas
I set up this party in a manner which will allow me to be flexible all the time. Against fast armies that compose of strong creatures that will do decent damage, I use the tanks - mainly because my defense is relatively low, being a mage. Against ranged armies, I use Paladins, Tirexes, Gorguanas, Inquisitors and Archmagi. Against mixed armies, I decide according to the composition of the army.
So far I've cleaned up everything up to verona. We'll see where it will go next.