This is great news! So a pseudo-archer team does work for a warrior on impossible difficulty.
12 rounds on K'Tahu, that's wicked.
Correct me if I'm wrong, but I'm guessing these three factors helped a lot in your speedy no-loss victory:
1) phantom paladins allow you to resurrect your troops all at the same time
2) except for maybe the royal griffins, your high physical resistance paladins and all 3 of your archers could concentrate fire on K'Tahu when there are no summons
3) you have a lineup of 5 full stacks
I haven't faced Baal myself, but I always thought K'Tahu was the tougher fight since you had Bill Gilbert's army to help you finish off Baal.
Just finished Elon atm, took Zilgadis no-loss in 39 rounds instead of the 67 rounds on my initial run-through (see screenshot). I am very envious of the 95% magic resistance (gift-bag items?) you had when you took him out in 6 rounds; I only had around 37% magic resistance.
Oh well, I probably wouldn't have been able to equip those magic-resistance items anyways, what with all the XP-bonus items I need to put on.