Id say the most Balanced Character is probably Johnny Cage.
Cage is balanced, but not in the sense of what he is good at across the whole board. For instance, he has insane rush down, but a good Sindel can and will give him a hard time if he cant get his combos in. In that sense he excels in one thing, sucks at another.
Sub Zero, Nightwolf and Sektor are all good examples of a well balanced, all round fighter. I don't think it was NRS intention to make Derp Lao what he became, but there you go. They DO listen to their fans and I expect them to do something to him (if only to asuage, raging fans).
By the way, nice analogy of Lao, Critical.
Ergh, Ermac and Smoke are a pain in the ass if you're a Sindel player like me. But a lot of Ermacs rely too much on his forcepush on wake up (easily punishable).
Smoke's INSANE teleport speed will keep Sindel out the air from throwing fireballs at him, and fighting a Smoke that runs away the whole game is very, very boring.
However, I pick NW and no one really bothers me on the roster.