She's super skill-reliant; it's actually not as simple as throwing out a Q W E R if you want to do the most damage, and she doesn't have any mobility and barely any escapes (she actually doesn't have ANY escape unless you consider the knockback a form of one). She has a strong laning phase and I wouldn't say she gets any worse as the game goes on, at least, not any more than all AP champions in general. The thing about her is it's really easy to poke people whenever they're trying to farm because her Q is AoE and has a 4 second cooldown even at level 1- she makes you pick between taking damage and getting minion kills or not taking damage and, well, not getting minion kills, and that's not to say she's the only one who does that; in fact, everyone should try to do that sort of thing, but she does it super easily. Her full combo on the other hand, is a little hard to manage if you want the most out of it. With max CDR she can do up to 1260 base damage on her ult, but that's extremely unrealistic and takes quite some build up. Overall I wouldn't say she's necessarily OP, and personally I kind of view her like Rumble- still pretty good, but nobody really considers her because she's subjectively hard to play to full effect despite how strong she can be if done right.