I dont think anything affects buffs or debuffs, but our damage songs are affected by int.
Dirges have more melee buffs, we have one for parry and one to increase slash/pierce/etc. While troubs do avoidance(?) and casting abilities. Dirges also buff DPS, while troubs do attack rate.
Dirges do a disease proc and noxious resists. Troubs do arcane procs and resists.
Dirges have fear for crowd control, while troubs charm.
Dirges also have a buff to increase the targets str and aggro gain, while troubs decrease all non fighters aggro.
I beleive dirges get some more debuffs then troubs, while they get more buffs. Also in the high levels dirges can rez.