Wow, playing with just two Heroes is gutsy, and one is the Wizard! Congrats on making it through. Are you playing Zargon as well, or is there a third player?
You could consider allowing the Heroes to take their turns again before a Zargon turn. That would get you back to the 4 to1 turn ratio bit still leave you with less Body Points and spells overall. Or you could just keep at it as you are. You'll likely face more party wipes, but the glory....
If you stay with two Heroes and get wiped later, you might want to houserule in a gold coin handicap for replacing lost gear. That way your Heroes will be better balanced for the tougher Quests. Then again, your method of selectively replaying Quests with no map alterations worked with the Trial, and that was a tough one.