@Ch7:
Save before going to the manor during the chapter. It automatically triggers a major angel battle.
Playing a macro game isn't really working out and I solved it with a 6 pool all in...
As my stock of potions are low, people would start dying if I am to play the defensive. So I just sent 1/2 of my group deep into their front to snipe the target.
Got to here in turn 4* with a swift proc with both Wil and Serawi, made the mission somewhat trivial.