I personally would say that right now it's:
#1: KO.
#2: Lumineth,
#3: Seraphon.
The recent Metawatch data came out before the full release of the Lumineth. Now to be 100% honest I have yet to play against them, but I'm not looking forward to it. I'm not looking forward to never being able to get magic spells off unless I bring Kroak, never being able to do anything to Teclis unless I bring Kroak and all his support units, *still* losing the magic game because Teclis can bounce it back on me, getting my heroes sniped turn 1 or 2 without being able to do anything about it, or losing the objective game to the cows and hammer elves because lol they can kick you off objectives and also have two units fight in a row. Lumineth at the very least *seem* to have only one weakness, and that is a somewhat low model count. They also *seem* on paper to be able to hard-counter Seraphon at the moment. This is just how it appears on paper to me, and I fully acknowledge that I could be completely wrong. I guess we can only wait and see how they fare when they start participating in tournaments.
I think it's only the Fangs of Sotek Kroak and Skink spam list that's truly annoying to play against, but I do agree that at least this one list is probably annoying for most opponents. All of our other lists have severe weaknesses that even armies weaker than us in general can easily exploit. But I think this has more to do with the way AoS is more or less "rocket tag" with the amount of pure damage and especially shooting damage that most top armies have right now, and less to do with them actually being "weak" lists. FoS at least has some ways to counter or endure the initial enemy onslaught and still be able to hit back.
You're right, I think that sometimes it appears that we downplay our own army's strength. I believe that's most likely due to this being a Lizardmen/Seraphon fan community, and we really do love our army. But as ardent fans I think the tendency is to look and see what could be better. Doesn't mean that we ignore what we have, just that it's human nature to always be looking for something better, I guess. I don't think anyone here actually thinks we're a weak army, but since we have a pretty safe environment to voice our wishes for what we feel could or should be it can definitely come off as overly negative at times.
I think a lot of the criticism of our own faction comes from the fact that currently there is only one truly competitive list, that being Fangs of Sotek with Lord Kroak and Skink blobs. A very large number of us are really tired of being forced to only use Kroak, Salamanders and Skinks if we want to win. The majority of our army is very sub-par in comparison. Doesn't mean it's not fun to play and you can't do well with it, but I think that people are usually attracted to the army because of the dinosaurs and the big, tough Saurus somewhat more than the idea of just running Skink hordes. We want to play Lizardmen, not Gitz. And the fact that more than half of our army is considered mediocre at best is a big turn-off to fans. But we're also loyal, so rather than give up and go play another faction we tend to voice our displeasure at the fact that Saurus and big dinos aren't a viable competitive army. Stuff like this annoys the Lizardmen fans because, at least lore-wise, we get nothing in AoS. Lord Kroak should be just as strong, if not stronger in-game than Teclis, Nagash, Morathi, etc. Our Saurus shouldn't be chaff, our dinosaurs should be able to go head-to-head with other monsters, etc. Seraphon have a single very powerful list and a bunch of just ok lists. Other factions may be considered weaker than our strongest list, but still have multiple ways to play that are equally good. KO is in the same "boat" (haha) with one massively OP list and the rest of them being very underwhelming, but at least their army is much smaller than ours so it makes more sense.
That, and like you and
@Canas were saying in the other thread a lot of the newer armies are getting a lot of "break the rules" abilities that while maybe not the most overpowered thing in the game, are much more annoying because there's literally nothing you can do about it. Lumineth are a very good example of this and that's why I believe they are OP. Not looking forward to the Umbraneth when they come out. Being shadow-based, I'm guessing we're going to be looking at a lot of army-wide negatives to hit, teleporting, and yet another god on the battlefield. Malekith will probably be just as annoying as Teclis and Morathi, if not more so.
Sorry for the long post, I know I get overly detailed sometimes