I find the whole +0 OB attack thing when parrying entirely logical...
If you are manipulating a weapon to actively defend yourself from someone who is making an active attempt to "hit" you, it's just as easy to fumble as it would be if you are concentrating on making an attack. So rolling "just to see if you fumble" makes sense.... the +0 attack also allows for the chance, however small, that the attacker's own attack places them in danger from your parrying weapon.... as they try bypass it. Again, taking a penalty on THAT +0 roll to avoid harm to another is always an option, but doesn't reduce the chance of you fumbling.
As long as only one roll is required, I don't see the problem.
