Mantises are a special unit, so they should perform better vs normal units. You wouldn't ask for Grizzlies to be nerfed because Anders' Scorpions lose to them. The problem used to be quite the opposite, where if you're playing as Forge or Isabel, you'll be able to pump out hogs faster and cheaper than Johnson could, their Ram would stun the whole group, and they'd be torn apart. I'll have to check again, but they can still have a tough time against other leaders who buff core vehicles.
I know this is kinda out of left field, but I think that Johnson mantis's need a bit of a nerf in some areas, they are too good against everything in mass to the point of being unstoppable with how cheap they are. I think a small nerf against bases and a smaller one against air would work, They should definitely do well against infantry and ok against vehicles, but right now they seem to good at everything. Again, from my experience so far, they seem to effective in mass.Manti crush hogs... like its not even funny. At lease in my experience. I agree that Manti need a close look at how good they are, unbuffed by Johnson LPs, they wreck a lot of different types of units and when massed with colossi, I haven't figured out a way of handling them. His army highlights the bad shape Cyclops are in and the fact that Manti can pillage air too compounds the power of his army. Just my opinion, but I struggle when Johnson gets a foothold. Maybe I suck (I feel like I have to relearn the game again because my old tactics suck now) but I struggle against Johnson.
Like the mantis, I think Serina frost ravens need a little look too. Though not really an issue for being an air unit, I think their frost beams are too effective in mass. Similar to the mantis, if spammed, they are very hard to counter, especially when they also do damage to the units while freezing them. I feel like they should either do less damage to the units or none at all. Again, this is from what I have experienced so far in MM.
These are just my opinions of the game, I am in no way a "top tier" player, far from, but on a general MM level, I am noticing a pattern in how people are play, especially seeing that hornets still are viable as a spam unit against any other unit minus spamming AA.
AV are in a bad spot altogether, with them currently taking heavy losses fighting even AA, so a buff in that regard is necessary anyway. Once they can do their job properly, it shouldn't be an issue. In the meanwhile, you should have little problem being able to counter using air early T2 with the cost reductions to Banshees and Hornets.
I get that Manti are a special unit, but so are colossi, and so are flame hogs. Flame hogs got brought into line, I just feel like Manti dominate hogs more than they should, even unbuffed against buffed hogs.
I have a 60 minute game in my history where I was playing a 2v2 against a voridus and Johnson (I was Spartan Jerome and my teammate was Kinsano). We could not crack the Johnson army at all. We tried multiple things. I can live with the mechs being better than other T2 vehicles, but they were crushing tanks too in combo with Colossi... maybe I suck (likely) but I would like their strength to be looked at. I will try to figure out how to link that game here.
More along the lines, when boosted with overcharge they are invincible and shred entire armies. Manti need to be looked at, they should be relevant, but they should not dominate infantry, air and T3 vehicles. There is another thread where the question about Johnsons mechs being some of the top Anti Air is a legitimate question.