I completed this mission, even though I managed my time terribly. As a result, I didn't have enough turns to defeat Godric in the 1st week. I had to attack him on the 1st day of the 2nd week. This time, his 2nd army only had 20 angels. And I was lucky – the enchantment spell on the angels worked on the 1st try, and Godric somehow forgot all his spells except for Holy Word.

Conclusion: it's easiest to defeat a heavily upgraded Godric in the 1st week using a phoenix. This will also make it easier to deal with Markel in the 6th campaign. In this mission, he didn't gain a single level and didn't visit any upgrade locations.