Well, I've been epically busy for the last couple of weeks, and I've finally gotten some down time to do my WFO games. So sorry about the non-action, I'm ready to get this thing rolling again!
A few points on the shooting Bishop: for one, Trebuchets + cannons auto-hit both the mount and the rider, so we should work out wound rolls on the Plague Priest for both the direct hit from the Treb and the cannon. Doubt he'll survive both of those. Also, the Rocket Battery has a rule called "inaccurate," where you place the template initially, then roll the artillery dice. The template moves that many inches directly away from the artillery piece. Once its position has been established, you roll for full-fledged scatter. So, I think I'm gonna roll for that now on the off chance that it doesn't completely miss the Hydra. Odds still aren't good though, but I may as well see what happens...