I did this last year, so someone else would need to confirm if my method still works. I completed the mission with Wukong + Sancti Magistar. You can equip any weapon for Primary, though I'd recommend weapons that have AoE capability (Kuva Bramma, Proboscis Cernos, etc.). Secondary is optional; however, don't use both a primary and a secondary. Use Sancti Magistar for your melee. Cast 1 (for your Wukong Clone). Then, for the entire mission, you can just spam Sancti Magistar's heavy attack (default middle mouse for PC) near the defense target. Your melee's heavy attack will heal both you and the defense target, so health should not be a big problem. I don't recall how long did it take me, but I finished the mission easily with the method I explained above.