Plot Armor is when a character escapes a dire situation without a believable explanation. Magna's case does not apply to this. His new power is well explained and has a huge drawback of needing half a year worth of preparation. Magna probably can't do jack squat to any Qliphoth Demon considering...
The amount of power in the Black Bulls far outmatches any other squad in the Kingdom.
Asta - Captain level+, possibly Wizard King level.
Yami - Captain level
Nacht - Captain level
Charmy - Captain level
Noelle - Possibly Captain level
Secre - Arcane Stage
Vanessa - Arcane Stage
Cool matchup, if we go just by the feats shown so far, I'd go with Yuno, his passive matter destruction should be too potent of a defense for Nacht's Pack. Even Hunting Grounds might not work because of Yuno's Mana Zone.
Hmm, depends. If Vanica can grant immortality to the whole Triad, then they cannot loose, the Schutzstaffel lack any way to negate that kind of ability.
Pernida and Askin are the weakest here. Neither can survive Dante's Singulary or Zagred's Demon Swarm. Even if Askin could somehow adapt to...