Not sure about Devices but I've been having a lot of fun with a Dark/Tactical Arrow/Soul blaster. I feel like a Controller with multiple single target holds, an AoE hold, an AoE knockdown, two AoE immobilizes and an AoE slow. With the Control Hybrid I can shut down groups, often lock down bosses with one ability cast and still pump out really good damage. Build Up + Aim with the Gaussian proc means Blackstar can obliterate most enemies in a group, and then I have it slotted so they take almost around a 45% to hit debuff so any survivors wiff on their attempt to retaliate afterwards. Plus almost all of my powers are inflicting to-hit debuffs on enemies which is a solid debuff.
From the primary I skipped Gloom. Gloom does solid damage, but I find that 3.6 seconds it takes deal damage feels too long. In most groups, especially at higher levels, enemies typically evaporate pretty quickly even when they're purple so between the cast windup and the time for the DoT to tick it feels like unless I'm hitting boss with it, the target is going to be dead well before the DoT deals more than a tick or two at most. And if I'm targeting bosses I'd rather be using a harder hitting attack like Moonbeam or Life Drain, or a Hold, or just using them as a target for my cone powers in order to hit all of the enemies around them. I felt like I had enough options that Gloom wasn't bringing anything to the table. I ended up preferring the instant damage from Dark Blast, plus with high enough global recharge it recharges quickly enough I can easily weave it into my attack chain, whereas Gloom has twice the cooldown. And if I need a big, single target attack I'll just use an instant cast Moonbeam (its cooldown is only 1/3rd longer than Gloom and it hits harder and deals all damage instantly).
For Devices, the to-hit debuff from Smoke Grenade will stack nicely with the to-hit debuffs from Dark. Obviously Super Speed (or a Celerity Stealth enhancement) with Field Operative will give you full PvE stealth, allowing you to easily get yourself positioned for setting up your cone attacks or getting into the middle of a group to pop off Blackstar. Umbral Torrent is fantastic. The knockback is useful soloing, but if you're planning to group then get a knockback to knockdown enhancement. As Devices you won't have any issue ensuring that Moonbeam will be instant cast (and when the new patch comes out that won't matter) so you'll be using it a lot. It can be a little expensive to spam though at lower levels though. Slot Life Drain for heal, it charges quickly and can heal you for a surprising amount of damage, plus it still hits pretty hard even without much for damage enhancements. Your AoE damage might feel a little underwhelming since Tenebrous Tentacles takes over 7 seconds to deal its full damage, and it's not uncommon for most minions to die before your tentacles deal all of their damage, but keep in mind that Dark's AoE damage is competitive with other primaries. Umbral Torrent and TT (assuming it can deal full damage) hit as hard as AoE's from most of the other primaries (Fire excluded of course).