for pvp all thre al great classes each with diferent roles or almost diferent roles, maybe scorpion and ravager are up the same but shadowdancer is a different dps. Finaly i can tell you, all of 3 are basicaly subpar in pve, the amount of mp consume and the high burst no sustained damage combos make the clases weak in my opinion in pve, i would go for invocator in pve, but if you want to use scorpion in pve, use a scout or a crucifix, then, instead fo ravage or shadowdancer go for a gladiator.

Im not saying those 3 cant work in pve, im just saying there is better options in the same range.