I'll have to strongly disagree with the Outlaw remarks. I think they are solid. Eradicating infinite fleas is actually a rather useful niche. However, by themselves, they're not intended to achieve much. They should always be working in combination with other things. I find outlaw, rogue and bandit are a good early game skirmishing (in the general meaning of fighting mobile, low intensity battles rather than the specific Zero-K unit function) combination while being resistant to raider and riot counterattack (Outlaw cripples the advancing raiders, meaning my own raiders can dispatch them with ease, rogues dispatch riots (albeit not as quickly as I like) and once raider or riots are dispatched, isolated assaults become prey as well). Despite its other faults, rogue outranges all ground skirmishers besides the Recluse, and can generally trade with them.
Despite its range, I think the rogue is the weaker link in shield fac, and it's not outrageously bad, just irritating on account of the slow rockets (more AOE at current projectile speed, or more projectile speed please!) Vandal is worse (I think of it as the FAAilbot), essentially the Redback of the AA category. At less than twice the price, the Gremlin instahits aircraft for nearly twice the DPS and packs a cloak that gives it fantastic utility as a scout as well
The Outlaw isn't by itself a hard counter to anything, except fleaspam. When it comes to Iris/Snitch however, a shield ball with embedded outlaws is much more difficult to get close enough to in order to inflict critical damage. Identifying the most viable angle of attack takes considerable time, concentration and APM- which must inevitably be diverted from elsewhere. The Outlaw won't kill the snitches, but it might deter them from coming in the first place which has the same effect.
Darts are good for most of the same reasons that fleas are good. They're utility units that can screen against cloaks and anti-heavies and especially Dominatrices (you can have 10 for the price of one Domi- and that Domi will not live long enough to capture more than one).
Hermits don't see much use in my game. They don't seem to have any perks at all, (at least Thugs which are otherwise similar, have the shield mechanics to spice them up). However, I think that's just a case of personal preference.
I'll second the general pointlessness of hacksaws though. I don't think I've ever built one. Unless you've somehow got metal to spare at exactly the right moment, you probably won't even get it up in time to stop the pack of Ravens from wrecking your comm.
Limpets seem pretty pointless as well. Why slow when you can blow?
Although I see them quite often, I don't think badgers are worth an investment. They only moderately outrange fencers, the mines seem to miss most of the time when do go off and don't hurt much even if they do hit something. A badger minefield rarely deters a concerted assault.
The Revenant doesn't seem to accomplish much for its cost either. Nimbus does almost the same DPS from far further away. The only real niche seems to be comm assassination and it doesn't even have that niche to itself (Scythe, Raven, both of which have more general utility as well) and the rocket volleys are so inaccurate they don't even hit structures that well which is what they're apparently supposed to do (which also erodes the volley advantage it should have for putting itself in more danger). Perhaps it would benefit from becoming a mini-Krow that goes to its target, drops a payload of bombs over a moderate AOE, but does so consistently and then pulls back to reload.