I'm curious; have you tried an offensive skill build?
I got impatient waiting on perfect drops for an all-red solo build (and I play 100% solo), so I crafted some Hard Wired which basically is all godrolled automatically (one stat slot is +1 skill tier, which is always the max, and the second you can recalibrate to a godroll you get off anything, and the rest of the statblock is the set bonuses). That, plus Coyote mask (for having nothing better), and a cheap-ass shitty chest with the 25% chance to reset skills on skill kills talent, and I'm off to the races.
I use Sniper Turret and Cluster Seekers. Sniper's the big damage source, but seekers clear out trash when having 8 guys shooting at you is a problem.
I haven't stepped into Heroic yet, and I'm still arsing around; I'm only SHD level 65 or so. My gear's not optimal (I did get a nearly godrolled Fox's Prayer kneepad shortly after swapping; one stat short but I can recalibrate it to be perfect). I have a crappy Acosta's Go Bag (60% ish stats) I should probably equip, and Hard Wired is apparently buggy and I'm not getting everything out of it I should. But I don't have the stuff to supplant it, yet. The Coyote mask is basically only marginally useful, and is in there because I don't have anything better.
Running Technician, though I'm likely to swap to unlock new specializations once I max it out.
Even so, I can clear Challenging CPs pretty easy. My biggest issue is when I get new spawns behind me, when a patrol comes back in or something. For a lot of CPs, if that doesn't happen, I can take the CP without using resources at all. Still have a lot of plans and stuff to get, so farming CP3s for them is what I do when I don't have anything else I want to do right now.
Named enemies usually take 3 sniper shots to get through the armor, without healing. Heavies take two shots to break their chestplate, and then a third for the kill. I can help by plinking with my M1A, but I mostly focus on clearing reds and purples and letting the sniper turret handle the yellows. Like I said, Cluster Seeker will also do a lot of work clearing out those reds and purples, which significantly reduces what you've got to deal with. Cluster targets where they currently are when it lands, so if the charges have to travel too far, they'll get out of the radius. But it's a pretty significant radius; it's more brutal in missions when you know where a spawn's coming from. Seeker can kill entire waves (and with the chest talent, can and often does reset itself).
My main rifle's an M1A with Lucky Shot; not a Baker's Dozen but the stats are good (not godroll, but highish). Using The Sendoff as my secondary, since that's one of the first crafting plans I got. This means the Ammo Hoarder directive is stupidly easy to roll with; I can clear fights without even using ammo, and when I do, I'm really efficient.
Would this build be great for group content? I honestly have no clue. But for solo? It's super safe, isn't all that slow (Cluster Seekers clear shit out, letting you focus on the yellows MUCH faster), and you can focus your skills on offense rather than having to run stuff like Revive Hive or healer drones. I'm underplaying how effective the M1A is with zero reds, too; I can still plink off red and purple enemies just fine, solo.
For heroics? I'm sure I could handle them. I've cleared Control Points at level 4. It slows me down enough I'm not sure it's efficient. Gear and SHD levels will likely change that. I really should use the Acosta's and the Fox's Prayer knees.