Most (I'm excluding Jaqui from this, as I do find her very dull) of the new characters are pretty solid in my opinion, they all offer something different and have good potential in design & moves. They all need some costume love though.
D'Vorah is inspired, really great in so many ways.
Ferra/Torr may need some buffs to their effectiveness, but as a concept character design it's really quite special.
Takeda is a nice design alternative to Scorpion I think, the game really needed another character for the legion of Scorpion fans to choose (like Street Fighter with Ken & Ryu) - MK online is in danger of getting stale when all you fight sometimes is Scorpion. It may not have worked entirely, but his moves share some similarities and obviously their story is linked, he may need a few buffs and could really do with some more interesting costumes, but the basic moves design and character are pretty decent and leave a lot of room to work with. I wouldn't mind seeing him become a classic ninja of some colour. The whips are a very cool combat design.
Kung Jin as well is a great new design and I think he fits perfectly. I don't particularly like using him, but I do think he fits into the MK world well.
Cassie has some of the more obvious flaws with the new characters and is in dire need of something interesting to wear, but she kind of does it all well and with a bit of flare and humour. She is fun.
Erron Black is for me like Kung Jin, I don't find him fun to use, but he fits in and his move set works really well. Nice character addition overall.
Kotal is interesting, has great potential that is just not quite achieved, but just a few tweaks would work very nicely.
I'm certainly not missing older uninspired characters like Stryker, or even Jade. The idea that only new characters are not the best designs is looking at the history of the game slightly skewed.