It seems quite odd to me that one of the most complained about moves has seemingly been buffed since its last iteration.
I'm not 100% but I think before it could not be canceled into guard break.
Now it can.
Why is this a problem?
Well it has to do with the stamina/exhaustion systems. Headbutt does no HP damage however, it does quite a sizable chunk of stamina damage. I would estimate about 45% of your entire stamina bar.
This move makes it incredibly easy to put the opponent in a near state of perpetual exhaustion between guessing to dodge the headbutt or tech the guard break.
Failing to tech results in an overhead heavy to the dome and still stuck recovering stamina.
Failing to dodge the headbutt and you're back in the mixup.
I think an easy fix to this problem without making headbutt a mere annoyance would be to significantly scale stamina damage down when exhausted so you can't abuse this mixup so leisurely.
Oh and I nearly forgot to mention Warlord drains your entire stamina bar upon a successful parry so he can start the mixup from that point as well.
You could cancel into a guard break last time, too. I mained it last test, and I agree with your point. When you're out of stamina, a Warlord can punish you so hard, almost always resulting in a kill. It's pretty insane in its current state.