Sopposedly, Dark Monks are the aggressive Monks and rely on dealing damage compaired to the Light Monks which are more deffensive. But, they both have the same DPS and AC. The Light Monks get nice spells they can cast like lesser restore, remove curse, raise dead, while the Dark Monks can blind and curse mobs. But the Dark Monk finishers, as helpful as they could be, dont last long. By the time I get off a finisher and blind a mob, it dies. So theres no real reason to use the Dark Monks finishers, unless I'm in elite high end quest. The finishers are much harder to get and still they only last a second or 2 longer before they get vorped/CONed to death.
I personally think there should be a line of enhancements that are damage dealing. Enhancements that increase To-Hit and damage on weapons, increase To-Hit and damage from elemental strikes, and Increase DC for finishers (these coulod just apply for the stikes, and/or increase the Ki needed to use them). Instead of Rise of the Phoenix and being able to rez, there would be an enhancement that would be similar to the Paladins Divine Light (6d6 points of damage to all nearby enimies).
You would still need all the pre-reqs for Rise of the Phoenix (1st tier of all elements and 2nd tier of one element), excpet the Path is different. The Ki would also stay the same costing 50 Ki each use. As well as a cool down, I'm not sure what the cool down time is for RotP, but probally would be close the the same time if not the same time.
Just my thoughts on what could be done to start the need/want of Dark Monks. Obviously, these ideas have lots of wiggle room, but hopefully it starts throwing some ideas around.