That null follow up though

Eh, I think I'd rather use a different B skill. Null follow up is too specific for my tastes.

A fast L!Hector can run Wary Fighter and QR (or just WF) and will probably be okay.

It seems like double QR wont cancel it out. The people who this would be good on are people like Libra, Nephenee, Kliff, fast tanks. I dont think anyone else should even bother with it

Null Follow Up, would be fantastic sacred seal. Not overpowerd, and sitiational. But we need some common strategy to counter 180 BST armored units.
It could even change meta because of how hard it counters armored with fighter skills.

I feel that skill is a great idea.
At first it seemed OP to me, but it uses the B slot. Meaning it works as equalizer.
You're robbing the enemy of their B slot power.

And we don't know the restrictions yet.