Why do champs with multi hit A1 use their single hit AoE attacks on the Fire Knight shield?

Mission to do stage 25 on auto. Team: Deacon Armstrong (lead), Coldheart, Visix, Armiger, Scyl. No problem to do the stage manual. 

On auto Visix uses her A2 and A3 on the shield. I could completely disable that skills, but that would make the fight vs. the waves very hard. Her A2 with ally protect and her A3 with provoke help a lot to keep more squishy champs alive.

Deacon uses his decrease def skill on the shield on auto, instead of his double hit A1. Why?

Coldheart, on the other hand, seems to be much smarter than other champs, she uses her A1 on the shield. Why can't other champs be as smart as Coldheart?

Please Plarium, change that mission from "do stage 25 of Fire Knight on auto 10 times" to "do stage 25 of Fire Knight 10 times" - or give the champs an AI that is able to do the stage I can easily do manual.