This deck is very slow. It's not that consistent anymore due to the lack of Twins and Sage's.
Doesn't have the same control it had with Chandelure, so you probably can't just get set-up and take 6 straight prizes without your opponent attacking anymore. It's much harder to keep the lock going.
It's easy to KO 2~3 Gothitas before you get one out.
If you do get the lock out, you will probably lose on time if it's a 60 minute top cut, and in Swiss you might lose because of time too since the deck is much slower than it was on HGSS-On.
Gothithelles are easily KO'd by Mewtwo EX, and you probably have limited your resources quite a bit, so it's hard to get another one out.
Since you'll probably attack with Mew EX, if they use Sigilyph you'll have to use Accelgor and it may be quite hard to get it in play again.
Also, the 4 N's that are usually played in every deck this format will easily disrupt you when you only have 3 or less prizes left, and even if your deck is very thin already, chances are that you'll probably miss the Deck and Cover.
I don't see this deck being viable anytime soon unless something like Twins is released again.