A-tier: Circle, Retribution, Cygnar
B-tier: Minions, Protectorate, Mercenaries, Trollbloods
C-tier: Legion, Cryx, Skorne
I have changed my mind a bit, especially following Una2, but by and large this is how I perceive the meta. Given Una2's power and her natural strength vs Mad Dogs I'd swap the two around. Anyway, it's not important for this piece.
In a competitive setting, it is all about the pairing you can make. Nothing ever exists in a vacuum. Many players make the mistake of evaluating the "inherent strength" of their list(s). Almost always when I'm consulted for advice, I ask: "What do you intend to play it against?". I don't care if you can do X, Y, Z if it doesn't help you solve the matchups you need it to. Threat range this, focus that. Note that for this entire analysis, I'm just looking at the best casters in the various factions. All factions have some fairly useless caster choices.
As I've written previously, my goal when I make a pairing is to ensure solid faction coverage. I want to have at least a list chicken situation, preferably a predetermined dedicated caster per faction (or at least pairing). So what is my reasoning for the tiers above?
Convergence will just struggle big time no matter what their pairing is. They will have glaring holes and especially against the powerhouse factions. I'm sad to see them this low. Legion, Cryx and Skorne are a little better off. Legion has some solid builds in Vayl2, Lylyth3 and Absylonia2 for example, but regardless of how you mix these you will have significant holes in your pairing. Cryx has Skarre12, Deneghra1 and Coven, but again we see some rather big, big problems here. Skorne has a single powerful build, Makeda2 kitkat. This is playable into a ton of builds and downright favourable against multiple of the powerhouse pairings. However almost everything else in Skorne is crap.
The next tier consists of factions which have fairly solid options but tend to rely heavily on a crutch or two to stay competitive. Minions have Rask, Protectorate have the High Reclaimer, Mercenaries have Ossrum/Magnus2 and Trollbloods have Madrak2. In and of itself the need to rely on a crutch doesn't make you less competitive, but these crutches are fairly polarized in my experience and the top factions have decent answers.
The top factions at the moment I consider to be Retribution, Cygnar, Khador and Circle. They all have a handful of competitively viable casters and can play a number of combinations of pairings with good faction coverage. These factions all have really solid options, ranging from Arcanist Mechaniks to Thorn, Rifle Corps Rocketeers to Sentry Stones etc. They also have some of the best casters in the game, e.g. Wurmwood, Haley3, Karchev, but unlike the tier below these casters aren't as essential to the faction's strength. Remove Karchev from the game entirely for example and I still consider Khador top 4.
So, Cygnar among the top 4. I think most readers will agree, and especially the most vocal opponents of the current incarnations of Haley2 + Haley3. However, let's dig a little further. Why was the pairing I've taken recently so strong? Haley2 excels at controlling melee lists. It's why she has game into Karchev. I believe many players hate her because they don't realize that this is her thing. When people try and play like Helynna into Haley2 and rage when it doesn't work I'm like "what do you expect?". This is exactly the kind of list Haley2 is supposed to play into. It's her strength. Haley3 on the other hand plays a completely different game. She plays the long game, the you-can't-trickle-me-down game. Ironically, kind of like Mad Dogs, but in a different way. Trying to alpha Haley3 rarely works. She absorbs it. The rolling cloud wall also enables her to buy time and space as well as counter a number of gunlines.
Let's take a look at how the various factions look from Cygnar's perspective:
Khador: Always hard. Butcher3, Vlad1 and Karchev all feel like they are on par with Haley2. Haley3 is iffy to drop vs Butcher3 and auto-loses to Karchev. Very even matchup if both factions bring their best lists.
Retribution: Issyria feels bad for Haley3, Ossyan is auto-loss for Haley2 with the right build. Kaelyssa feels like she has game into both and vice versa. Haley2 feels up against Issyria. Haley3 feels like she has game into Ossyan. I think all other casters in Retribution are in Haley2's favour. Depending on pairing, this can be anything from list chicken (the worst matchup is Ossyan vs Haley2) to Cygnar favour.
Cygnar mirror: Caine2 and Sloan can be really tricky to play against. Haley2 mirror is very hard for both sides. Haley2 vs Haley3 feels like game for both sides. Haley3 mirror I've never played. Cygnar mirror is typically tricky almost no matter what.
Circle: Wurmwood feels really bad for Haley2 if the Circle player has experience with the matchup. Haley3 has game into him but it feels a little uphill. Not a lot so but definitely not in Cygnar's favour. Una2 is very hard as well but again Haley3 feels like she has game. Kromac1 is very good against Haley2. I have fairly little experience vs Baldur2 so not sure about him. Kromac2 is in Cygnar's favour. Realistically, Circle tend to drop Wurmwood and as such are favoured in my opinion.
Minions: I originally thought this would be a Haley2 matchup but it doesn't feel good for her at all vs Rask. Haley3 on the other hand probably is up here. Not sure how she fares against other Minion casters.
Protectorate: An iffy faction to face. High Reclaimer can feat and kill Stormwall whenever he wants basically. If you don't get a scenario which is fast with decent terrain I think Haley2 is down here. Haley3 feels solid into High Reclaimer but she's not favoured vs Amon I think and definitely not against Severius2. Depending on pairing this could largely be a list chicken situation.
Mercenaries: As Marcin taught me at ClogCon this is a Haley3 drop. My experience with her against both Rhulics and Kingmaker's is limited. She feels ok into Cephalyx.
Trollbloods: I don't have as much experience here as I would have liked. It feels like Haley2 has game into most (all?) of their builds. Haley3 I believe struggles with Madrak2.
Legion: Always a hard matchup. In my experience Haley2 just dies. Haley3 has game but it's hard. Guess that goes both ways. Feels even ish, perhaps slightly favoured for Haley3. Legion needs Vayl2 or Lylyth3 though in my experience but then again doesn't their pair always include at least one of these?
Cryx: Haley2 does not like Deneghra1. Haley3 is ok into most casters though. Coven is best against her. I don't have enough experience here but from what I gather from others it's a very close matchup.
Skorne: Haley2 struggles with Kitkat. She simply doesn't have the volume to deal with them and she's exposed to dying. They'll also jam sufficiently to block any assassination angles. Haley3 feels good into most builds though, have yet to run into any problems with her.
Convergence: Haley2 matchup I believe. Have yet to experience any big problems here. Mother can try and play a drawn out game and look for openings through backlash, but apart from that I haven't encountered any real threats. Even when I've messed up big time I come out ahead with Haley2.
So if we assume that everyone brings an a-tier pairing, it typically looks like this:
Haley2: Khador, Retribution, Trollbloods, Convergence
Haley3: Circle, Minions, Mercenaries, Cryx, Skorne
Both: Cygnar, Protectorate
The only cases where I feel like I'm up based on faction strength are Trollbloods, Convergence, Cryx and Skorne. I consider all of these factions to be seriously lacklustre in the current meta. Thus, whether Cygnar's broken or they are just too weak is a matter of perspective I guess. However, against everyone else it feels like an even-ish game. I believe this is Cygnar's main strength. Against most factions, we don't pose impossible questions. We don't have any games which feel like the steamroller-experience we had in Mk. 2 or which mad dogs or angry birds have against some factions in Mk. 3. What we do is that we seem to always have options. We always have something which gives us game. That is incredible as nearly everyone struggles with some kind of weakness. However the same holds true for the other powerhouse factions. I currently believe Circle is S-tier because a Wurmwood/Una2 pairing has game into literally anything and against -many- factions it's way, way up for Circle.
What I would like PP to do is try and find the matchups that are even and try and balance the game around this. Currently, there are a few casters way ahead of this curve and there are a ton of casters and a few entire factions too far behind. I hope they push from both sides at the same time. I also hope they try and work so that all factions have decent answers against all other factions within a 2-caster pairing. Right now I think there are too many Rock-Paper-Scissors effects in play, i.e. some factions might have decent answers to X, Y and Z but X, Y and Z are too far apart to cover with 2 casters.
To summarize, in my experience my pairing is rarely significantly up in a matchup. When it is, it's typically against one of the factions I consider to be weak in the current meta. However Cygnar has excellent coverage which is key to overall faction strength. On top of this, Haley2 and Haley3 have amazing angles, there is almost always something you can do. The skill cap is very high, but the skill ceiling is infinite.