The Shadow Caster Nightblade, master of stealth, battlefield control and destruction, with a near endless supply of resources at his disposal the Shadow Caster can let loose his entire repertoire as he feels the situation demands it.
(I currently v7 and have had no difficulty smashing through content. The build uses mostly siphoning skills with a minor support from restoration and destruction skill lines. The negative buff removal and ability to endlessly spam incombat stealth due to high resources and resource returns/regeneration, means you can solo world bosses and almost anything.)
The build:
The Shadow Caster employs some of the strongest Area of effect damage this game has to offer through his Lotus Fan initiation (area snare, damage, and damage over time), into Power Extraction (area damage, weapon damage increase per target hit), into Pulsar (heavy area damage, reduces enemies max health by 10%) and finally, if the situation deems it necessary Manifestation of Terror (Area Fear).
The Single Target capabilities of the Shadow Caster boast constant streams of resources, healing and battlefield control. You will engage your victims from range, but you don't fear being up-close, so strike where you feel you need to. Letting loose your barrage on the enemy starts with Crippling grasp, rooting your target for 1 second, before siphoning his movement speed (snaring him) and sending it to you (speed increase) while also doing heavy damage over time, keeping this ability up ensures battlefield control and a nice source of damage. From here, the shadowcaster will buffet his enemy with a barrage of Funnel Health volleys giving him health while demolishing your unlucky target. Once you feel you have let the target suffer long enough, finish the job with Impale, or if you feel like really devastating them, use soul assault which will literally turn them to dust before your eyes.
I chose restoration staff for my single target dps weapon for the +10% damage passive it gives me, it works wonders on the ultimate and single target damage. When I am questing I have stealth on my bars, when I am in dungeons dpsing, Ill swap that out for impale (the ranged execute). For my aoe bar I went with the destruction staff, as it is simply king of area dps, and synergies well with power extraction.
I leveled the restoration tree as well, so I can queue for vet dungeons with minimal wait times, and also play with friends if needed, it just requires a quick 2 second skill swap and Im ready to go.