s. C is good on the outside, but it's uncomfortably slow at its minimum range (where you risk the very awkward transition to close C and the different timing it requires to AA; hit it early expecting a far C, and you get a too-early close C that misses its own active frames and plows right into the opponent's). Safe on block, but the low pushback means they're still uncomfortably close to Mai, and none of her advancing (walk-up to intercept), retreating (walk back/jump back), and stand-your-ground (vertical jump/stand still and bait) options seem good at that range to me. Half the time when I try for a s. C that I swear will win, I get clowned by something stupid like Shen early hop j. CD.
She has a very hard time winning trades to me where C is concerned, and the move seems like a waste pre-emptively. At that range, unless they're painfully stupid and I know they'll land on it, I'd rather do s. D or make them whiff with anti-air c. B.
s. D I have slightly fewer complaints about because of the slightly superior horizontal range. Harder to get a close D, and you don't feel so bad for not getting a bite preemptively because you outrange a lot of lows and the pushback is a bit more comfortable. It's good but not godlike. That's what I'm saying.
And mostly I'm thinking about her air normals when I say her normals are oversold. Her air normals have always been one of the biggest things she's had going for her on a fundamental level -- get a fan safely on screen and lock off air space with her fast jump and fast attacks. Her jump arc and gravity are up to the task, but most of her air normals aren't in 13. Much harder to clip limbs now unless you just don't give a fuck (a bad philosophy with a low-return character like Mai IMO) and hit a button ASAP. Waiting even a little to play hitbox games gets you creamed more often than not by people just thrashing in the air.
The only trick to beating Mai is just getting in, and her idiot-checks while zoning aren't particularly fearsome unless she has NeoMAX. Early hop attacks own Mai IMO. Just respect her fireballs getting in, put her back against the wall, and soon enough you'll be close enough to squeeze the life out of her. Take the trades, her reversals are limited and expensive, and you're still right in her face where her anti-airs are crap. One good combo and you have a great lead on her; you need to do something REALLY stupid for a low-damage character like Mai to come back on you.
Mai's bullshit is mostly useful against the inexperienced IMO. She clowns impatient players, but loses badly to people who don't throw their controllers whenever a fan hits them. She's fun and she's still one of my favorites, but she's definitely not that great.