Second update:
The build hits another period of low efficacy immediately post-Depot A, roughly level 10-12. This is probably just due to Dominating being, you know, Dominating, but most human enemies you encounter immediately after Depot A are too sturdy to take down with just a few spear stabs, which becomes a serious problem when there are 3 or more people with guns. (For reference, I'm basing this assessment off of the bandits a few screens north of GMS (the ones that charge charons), and the gangsters guarding the Tunneler.) The addition of an Electroshock generator on a tungsten spear has helped a ton with damage when Impale is on cooldown, but my god it is incredibly hungry for batteries.
Part of the issue I seem to be running into is that spears' related feats are oriented towards defense, not offense. Without Impale, it's generally hard to do enough damage to finish one person a turn, and if you fail to finish the job they heal up, retreat, and fire at you from a distance. Chasing down the wounded is tough, partly because spears are a 20AP attack and partly because their friends are going to be firing on you while you do it. A lot of bandits also have high enough dodge that you need to use disables on your current target, not their out-of-range friends shooting at you. Again, the absence of Dirty Kick in this build is proving to be tough, and it's even more noticeable now that flaming barrels protect all those pipeworking bandits from being Cryostasis'ed. Unfortunately, spears are only a defensive weapon when you're up against melee attackers, and damage is high enough in Dominating that a PSI tacvest (18%DR/11DT) and efficient (670 health) med. shield don't cut it.
However: things have gone substantially smoother since hitting level 13/14 and shifting from tacvest to tungsten tin can. It was a bit time-consuming to track down quality metal plates since I haven't tackled Foundry's little animal control problem yet, but Core City merchants finally came through. Between Armor Sloping, Nimble, and some low-to-mid quality boot springs, I've got about 20MP on 67% armor penalty, with mechanical defense sitting at ~52%DR/28DT. I have also finally been able to invest 55 points into Temporal Manipulation for PTC, which not only improves mobility but increases damage output by 50% on turn 1 - it even lets me recharge the battery on turn 2.
Some other thoughts on this build:
I have basically never used the shotgun whatsoever. It seems interesting in practice, but it's the same AP cost as the spear and its effective range is much shorter than I remembered. This might just be dealing with a lower accuracy than I'm used to, so my assessment might very well change if/when I put a couple of spec points in Versatility and pick up Leading Shot. However, right now my default is to just walk the extra couple of tiles and poke my opponent with the spear. The high AP cost of both shotgun and spear also creates problems when trying to finish off a low health enemy (or, say, kill a Burrower spawn). I'll probably craft a low caliber assault rifle or SMG to bridge that gap; a knife or something might also be pretty useful.
I am intrigued by the Spear Throw feat, but the fact that precision scales off of throwing while damage scales off of melee is kind of troublesome. It may be workable to flashbang or Cryostasis an enemy prior to throwing, but that seems expensive and a little too conditional. On the other hand, Spear Throw might be really interesting on a Psychokinesis user - between TK Punch, Grounding, Electrokinesis, and Imprint, there are at least a few ways to reliably eliminate evasion at range.
In general, Psychokinesis seems like it might have been a better PSI path to combine with a spear. Both help trigger Opportunist damage, but there's a larger variety in PK. Cryokinesis is expensive in terms of AP, and it's not really feasible to attack all the targets that have been chilled by Cryo Orb. Force Field would be a huge help in corralling enemies so that I don't have to run after them. Combining Psychokinetic Chain and Sweep seems fairly conditional but also potentially very funny. On the other hand, trying to fit all of these different abilities in might feel very pinched with only 5 slots - some other part of the build would probably have to go.
I hope this kind of breakdown is useful for anyone trying to develop their own build!