She's by no means bad last I checked, but there's people who can do her job better (although with a different toolkit). Thing is that people always rush to who's the meta picks and that makes people think they're the only viable choice. EG: for ADCs Tristana and Lucian are the top 2 picks, mobility, early game damage and most of all they make good use of all the AD items after the Bloodthirster changes. Also keep in mind that for a while Lissandra was an extremely prominent pick in Top and Mid, so by Riot rules (and people rushing to meta picks as I said earlier) they had to make changes to her so people play other champions.
The meta at the moment's not the best place its been in, but it could certainly be worse by my standards. Nothing was worse than the 5 minutes 3 man side lane pushes.