Well, there are many reason of why she sucked so much in mk9…. Slow start up projectiles, unable to connect her fastest normals to full combos, so many bad match ups…..On the other hand some of her tools were rockin: d3, sweep, shadow GLOW….a few people say that is heavily rewarding to win when using Jade, and i totally agree. BTW in UMK3 she was really tough.. Anyway. Should a character be treated accordingly to his play style in specific games? I don't know…
Sub-zero also sucked balls in mk9 , but his importance as a character in the whole mk universe is more than huge.( tired to see him bodied so much, even in the late trailer)
Jade of course is not as important as him story wise, but she has some serious connections with other characters( Kitana, Sindel, Tanya, Shao kahn, etc.)
Personally i would like to see her return because I mained her in every mk she appeared. However, if the story changes so much and exclude Kitana (Huge mistake if done) then Jade probably won't be there as well.