When hitting a human target with the Poison Arrow, the knockback from the arrow seems rather extreme (it seems to be as rediculous as the currently bugged knockback from the Mauler Alternate Fire). It should be much smaller than this.
Update: This applies to all projectile weapons in any of the Doom engine games that knockback the target, such as the Doom rocket launcher. The knockback that the enemy (or corpse) seem to get is rather large and should be smaller.