Now, unfortunately, there haven't been many models released for the Farrow but let's look at what the other Hordes factions bring to the table (very generally) to see what kind of unique niche the Farrow can offer:
Trollbloods - Attrition, synergy, "combined arms" approach
Circle - Fragile, precision/scalpel, movement, utility
Legion - Ranged, 'Beast-heavy - expensive but efficient, high offensive output, elemental (fire, cold)
Skorne - Melee specialists - high damage output, "bullet" heavy warbeasts, melee support spells
Gators - Anti-"living", anti-infantry, attrition
So where does that leave Farrow? Well right now here's what we can gather from the limited information on what has already been released:
High Damage - War Hogs have an incredible damage output for only an 8 point warbeast and even Farrow Brigands are impressive when you consider their guns and melee weapons compared to other 5/8 infantry.
Slow - Farrow suffer from moving slowly. War Hogs are only SPD 4 and that makes them difficult to bring to bear. While Carver can mitigate this a bit with Mobility, not everyone can (partly why he's so much more popular). Also, the "Road Hog" can speed himself up quite a bit but he and the others are...
Defensively Fragile - While it's an interesting mechanic, it's a problem that to get the most out of the warbeasts you need to damage them first - especially since their 12/18 statlines don't inspire confidence in their defensive abilities. The infantry are similarly unimpressive defensively. Another reason why Carver is so popular - he turns them into DEF 10 but ARM 21 - much more resilient to a wide variety of attacks. The infantry are similarly fragile but at least they are...
Tough Infantry - Like I said, the Farrow infantry are not great defensively, but at least they are all 'tough' which will make up for it a little bit. While they might appear similar to Trolls in this regard, Trolls have access to better defensive stats with synergy support and all sport medium bases (Trample resistance) while Farrow have Tough to almost make up for their poor defensive capabilities.
Lack of Magical Attacks - Well I guess they do have Bone Grinders, but they are only shooting a POW 11 shot, which will hardly help them against more than one Incorporeal model. Of course every warlock has a magical weapon (except Arkadius) and an offensive spell, but they range from expensive (Carver) to conditional (Arkadius) to overkill (Drang).
So what could the Farrow use to give themselves an edge against their opponents? They already have two heavies and a light which are quite flexible in their usage, so it seems like they need some other elements which will help them out while making sure that they keep a unique niche in Hordes.
Offensive Animi - While there are rules about using Animi offensively, there aren't any offensive animi yet. The argument is made that giving another offensive spell to a warlock is difficult to balance, but in a faction like the Farrow, which is both small and new, it will be easier to balance later on if they include one sooner rather than later. Bone Grinders have an interesting magical feel to them and I think that the primal magic that the Farrow use could be interesting if it were channeled into a warbeast of some kind and would help the Farrow deal with incorporeal models better. It can be a really boring offensive animus, but I think Arkadius would welcome having another offensive spell besides Primal Shock.
Ranged Support - While Legion already has lots of ranged elements, they typically rely on their special abilities (Eyeless Sight, Hunter, etc.) to make their shooting frightening. It's also easier to shut it down if you have elemental immunities. Why not give Farrow raw damage output on their ranged weapons? Not many Hordes factions can play the ranged game particularly well or efficiently and the Razorback Crew and Brigands already sport higher-than-average POW ranged weapons, why not give them more of that? Perhaps a heavy warbeast sporting a POW 16 shot? Or what about a Farrow infantry unit with Slug Guns? Maybe a ranged-support animus (something not seen yet), UA, or solo? I think a solo with Artillerist will be a Gun Boar's best friend (especially with Targ around!). I also think it'd be cool to see a ranged heavy that, like the other heavies, could take D3 points of damage but to increase the RNG on it's gun.
"Charging" Support - While Farrow are a little slower than other factions, I think that they still need some speedy elements with a unique approach. They already have Massacre as an animus so why not include other animi/support that improve charge distances/damage? This way they still have a weakness (anti-charge effects), while still having useful tools at their disposal, and being true to the "feel" of the faction. Bounding, for example, would be a great animus for the Farrow to have, without being broken (it doesn't grant Pathfinder, for example). Some other abilities that might be useful would be granting Pathfinder on a charge, Powerful Charge, Brutal Charge, or even Assault.
Anti-non-living/Warjack - Right now the 'Gators probably do the best against living models amongst the Hordes factions, but there aren't many abilities which specifically do damage to non-living models like constructs/warjacks or undead (Mohsar and the Slag Troll, Storm Troll against warjacks). Many have discussed that undead is an underpriced ability and grants many advantages. Why not give the Farrow some new abilities against non-living models? Finisher is already a great ability against a range of targets for the Slaughterhousers, but you'd figure that the Bone Grinders might have something to use against undead models. This should probably come in the form raw damage, but why not have a unit like the Circle Bloodletters that can choose a different damage ability, with one dealing an extra damage die against living and undead models? What about a solo that can cause Disruption to a warjack? What about an animus that grants an additional damage die against constructs? If you give the faction something to deal with these models then perhaps Arkadius will see more play.
These are, of course, general thoughts that I've had and I'm curious to see what Privateer Press plans to do with expanding the Farrow faction. Right now it's really shallow and I think that's a real shame. No one really sees the Farrow in tournaments and while I understand why, I think it'll be better for the game as a whole when Privateer Press fleshes them out a bit and gives the tools they desperately need.