How is she countered by hard engage? She can just slow/speed away from them with her W and ult if they get too close. The only engage champ that can get on top of her is
but that's just how he is.
She isn't countered by long range since she can shield poke of stuff like Xerath or Jayce. She isn't a support yes I get that, but she does the same job as one even though she's a midlaner which is fine but then she has the damage of a burst mage. She has the best of both classes.
In lane her burst isn't that high, but all she has to do is QW and AA if she wants to and shield if they fight back for a win. Rinse and repeat until you can catch them in an ult. Even if Anivia/Vel'koz have more burst than her she more than makes up for it with all the utility she has that makes sure she's relevant if she gets behind and is just stronger if she's ahead.