Honestly really disappointed with the specter. I was already iffy on the idea of a spellcasting thief, but I decided to go with an open mind when trying it out.
The main issue is that it doesn't feel like a thief. It feels like necro got bolted down onto a thief. Cast times and cooldowns and overall it feels very clunky and slow. It doesn't feel like a thief-flavored support caster, it feels like purple necro. The character doesn't feel nimble, the animations don't feel nimble, and the skills overall feel slow and clunky and basically everything I try to run away from when I pick thief to play.
On top of that, the skills are all so convoluted! There are so many conditionals and clauses to it, it's hard to wrap my head around many of them. One of them (I think one of the dual skills) had a tooltip so big it didn't fit my 1080p monitor! Please streamline them.
I think a support, magic-y thief can be done. The shadow shroud ally tethering was actually much more intuitive than I expected. But I think a lot of work needs to be done to make the profession actually feel like an extension of thief, and not like you ran out of ideas so you bolted a scourge on my back and painted it purple.
Also for the love of god, give the auto attack a new animation. Whacking the air to throw tennis balls looks so bad. Give it some flourish, some flair, make the thief do some spins or something. Casting magic doesn't have to be like I'm hurling a rock at my opponent or playing whack-a-mole.