I'm all about Quan Chi! He's my main right now and I'm practicing him exclusively. I figure if he's as bad as some of you seem to be saying then I'll be able to play that much better with a more effective character after all this practice. Regardless, I love him and I'm not that concerned about how good he is or isn't because I think he's fun and cool.
Tactics I'm working on (I'll try to avoid combo talk):
For combos I'm using a starter, either (B+3, 1+2) or (1,1,2). Which to use depends on whether you want to start high or low. (B+3, 1+2) is excellent because I think it's hard for the opponent to block both hits (high then mid) giving you a good chance of breaking their block. I continue the combo, and from trance I either do (B+1, 1, DF1) for style or (1,1,teleport) to stagger them.
I'm trying to work in the stagger state because it looks like there's potential there for creating easier openings on the opponent. Landing a teleport puts them in stagger state, so from there it looks like they have to guess on whether I'll go high or low, making a second long combo likely!
I need to start practicing hitting the EX trance rather than regular trance. A friend I play with often seems to get frustrated at being in the trance and breaks my combos from there, so I would love to nail the EX trance in the combo to reduce his meter. I juts forget to because I practiced and learned the combo using the regular trance and forget to bump it up to the EX version out of habit.
I also want to practice checking the opponent with ground bursts a bit better and using the teleport more effectively, but practice is already paying off and Quan Chi is a blast!
Bonus story: my friend Jon and I were playing a tag match against each other. Jon's first fighter (let's say Kano) has a sliver of life left and he's across the screen. I input DBF1+block for the EX long range blast. Quan Chi stands up, points his finger commandingly at the ground and yells "BUH DEH!" or whatever hilarious nonsense he says and Kano gets knocked out of the park. I laughed so hard I could barely finish the match. Quan Chi is so rad