The part where you bust in to the fake golem workshop, in my opinion.
If I had no upgrades, I would have to choose:
Festus--Healer, with great mobility.
Dorgon--Range attack plus mobility that is superior to everyone else if I had no upgrades.
Darkling--Speed 9. Great as a finisher to weakened enemies.
Guy--Nice addition to firepower (excuse the pun) since Darkling and Shadowboxer only have Mind Blast, which is quite useless.
Grotius--Good attack that hits two spaces, 7 speed and plenty of health.
Anya--Without upgrades, two healers are a necessity.