I agree, she’s def not in the lower part of the mid tier. I think shes definitely in the top half of the cast.
She’s used in every team i main, and she’s easily my favorite character to play.
Yeah it sucks that shes got no super good stuff, but at the same time, its just a bit more of a challenge, and it means that not EVERYONE is playing her.
Lets look at her stuff:
with any hit, low kick, low punch, whatever, she can link into her qcb+KK super. lk lk LP shoryu xx either qcb+KK for the damage or qcb+PP for the DHC goodness (since even if you DC, all of her fireballs come out anyways! too good!
Against people that jump a lot and try to hit you in the air, qcb+PP stops them dead for good damage.
Hurricane kicks are crazy damaging. They allow for the sent infinite.
After a lot of air supers, you can DHC into her qcf+PP super for crazy goodness, and that super pretty much gives any other super guaranteed hittage (try doing her super and DHCing into Mag’s Tempest to see what happens)
Her assist is pretty good, the dash reaches pretty far and allows you to run up and get your offense on. Its also good to stop other assists, as it sends the assist character flying, unable to be used.
And while i’m not a fan of it, some people like Dark Sakura. If that’s what you’re into, go for it. She’s good, just not worth 3 bars, especially when i have Storm on my team. 
If you’re interested in her and have fun with her, then i say go for it! She’s a bit diff in the vs series than she is in most other fighters she’s in, but i like her best in MvC2 than any other game she’s in (though i dont really play CvS2).