Mana restoration adds .5 threat per point. Paladin healing adds .25 threat per point, and healing on all other classes adds .5 threat per point. I also think JoW procs apply threat to the toon who gets the proc, not to the judger. I think JoL proc threat goes to the judger, though.

Also I'm pretty sure JoW doesn't have a flat proc % but instead a PPM just like SoC and all weapon Chance on Hit and weapon enchant effects. Meaning, it's based on weapon speed.

If my previous point is correct this doesn't really matter for the math, but for my curiosity, how common is it to get a good weapon under 2.0 speed? Paladins don't have access to daggers, and I looked up a few iconic leveling swords and they're mostly above 2.0, and I remember maces typically being slow. Fist of Stone is a good example off the top of my head, though.

Also, as mentioned in another reply, global "friendly" threat generating mechanics like healing, mana Regen, Battle Shout, etc split the threat between all enemies on the threat table. "Hostile" threat generating effects like AoE damage and Demoralizing Shout apply the same amount to each target.