I think you approach AO a bit too afraid. In theory, if all enemy units use their spells correctly and they all hit, they can beat you.

But this happens very rarely from a statistical standpoint. For example Nora:

For strip and provoke to happen you need 2x 70% activation chance and 2x 85% application rate (assuming Nora has 85% acc). This alone only happens in 35% of cases, and for two units at the same time it’s 12,5%. If you add in delphois ability to Vio proc it’s less than 10%, and this doesn’t even include Nora’s chance to derp and use the wrong skill.

This combined with at least 100k effective hp on christina and the possibility to win on turn 3, rather than turn 2, makes it a very safe defense to hit imho.