Honestly that's become a rather big pet peeve of mine, Leona's just never been able to get over her initial stigma from the first impressions. I play with a rather decent Leona player quite often, and really, she has several BIG advantages that people just hardly give her credit for.
I suppose I'm no expert, so I won't be the most convincing voice, but I think she has some major advantages going for her; a fast overhead that goes over lows, a unique projectile that has amazing recovery which covers the hop arc and makes it near impossible to jump over safely (lest you risk a free V-Slasher), Several fast and forward moving pokes, fast movement speed, and almost complete control in the air to name a few.
Are there some do and donts specific to playing against this character?
Much of this seems to be character specific, but I think first and foremost against a watchful Leona player is to resist the urge to jump/hop unless they are completely unsuspecting(pretend it's Street Fighter, lo), because her air gimmicks, air-to-airs, and anti-airs are numerous and they'll usually hit very hard if she has meter. Also be cautious about anti-airing her because she has multiple ways to maneuver in the air (she has some of the best air normals in the game, an air special which is punishable, but will move her out of harms way, and an air super which will chunk you for trying).
It's clear that her weakest front is the ground, where all of her specials now have clear weaknesses that are important to understand:
- Moon Slasher is extremely fast, but has an easily punishable recovery. Treat as you would a reversal.
- Baltic Launcher will destroy any jumps or hops, and is VERY plus on block, but can be low profiled easily with a cr.lk or sweep
- The earring is similarly good for controlling approaches and starting pressure (also plus on block), but there is an area when it is at the top of it's arc where you can crouch under it and punish.
- For Grand Sabre, you just need to know that the short one is punishable, and the long one is neutral, but can be easily stuffed
- X-Calibur can stuff counter-pokes after blockstrings, but is punishable, the EX has a ton of plus frames, I advise GC rolling if you start blocking it.
After knowing all the tricks associated with her specials, you can focus on beating our her pressure game at neutral. her overhead is unsafe if she ends on it, and the special she can follow it up with is even worse, but her light attacks are hell on block and very fast(+2 on block on her cr.B >_>) and the sweep recovers quickly too (and I think it's whiff cancellable, not certain). I'd advise avoiding her jump in's if you can, because it's rather difficult to get out of her pressure once it starts.