[HoneyBadger]

I'd try dividing the poison damage and the arrow damage into two separate weapons-the arrow might do 3, 5, 7, whatever damage, which in the case of crossbows would be AP, while the poison weapon might only do 1 or 2 or 3 non-AP damage (depending on the bow used--or if you want to be really slick, the type of ammunition), and then add weak poison to the second weapon, but reduce the Precision for that one, so less poison would actually get through. So you'd have your first arrow calculating hits at say 10 Prec., while the poison element would be flying at 6 Prec, and not doing nearly as much damage, none of which would be AP, but when it *did* hit, it would automatically do Weak Poison.