Of all the Ninjas, I respect a good Scorpion. Sektor is also pretty cool. All the rest of the Male Ninjas...ack, I dunno...they all seem so lame and cheap to me.
Cyrax is nowhere near as OP as he used to be.
That said, the biggest combo I can get with Sheeva, using two bars, is about 50%. You expect it with her though, and it's a huge risk as she needs meter also for breakers and EX Walking Grab.
I like what Critical says about "conditioning". You really have to think ahead in this game. A Scorpion hits you with his overhead. So you think, "Okay, i'll block high" and he gets you with the low kick into spear. You HAVE to anticipate stuff like that. Most Scorpions, even good ones usually start with the overhead and usually go for the low poke second. The best way to beat a Scorpion is you have to do to him, what he does to you. He's a bit like Cage, you cant give that character one inch or he'll stomp all over you.