Yeah.
To be fair I'm kinda going through a rough transition. My main is jiggs, and going from jiggs to ANYONE is a huge change.
No one plays as Shiek. >: And I thrive on playing characters that are rarely chosen, so naturally I'm playing as Shiek now. She's really nerfed though. I mean at first when I saw/heard this I was filled with glee because of her/(his :D) ******** brokeness in melee, but now I feel kinda bad for her.
So far I've gathered that her only way to actually kill people is Upsmash and Sidesmash.
She has no edgeguarding game that I know of. (At least nothing like jiggs- I should stop.)
Her whip seems useless for everything except recovery. Needle storm seems to be only good for annoying people.
Halp?
As a Sheik main since Melee I can't help but take most of what you just said very personally and because of this I'm very tempted to not even answer any of your questions, however Sheik needs every user she can get to prove to the community that she doesn't suck and in fact is better then a good number of the characters in the roster.
To begin let me say that in order to get truly good with Sheik the first thing you will have to learn is how and when for each opponent can you get them into a tilt lock. What a tilt lock is in general is the repeating chaining of ftilt into more ftilt before your opponent is able to escape. Before this can happen you should always end it with something big such as an utilt or smash attack.
Sheik ftilt and dtilt both have a sweet stop at the end of the attack that allows you to easier combo your opponent if hit.
Needles this time around are very useless as a gimping tool and are now mainly used for racking up a quick 16 damage or to force your opponent to come to you if possible. They also no longer have priority so they can't cancel projectiles; however they can interrupt any attack including Meta knight tornado.
Sheik best smash attack as far as killing wise is the upsmash as if you hit someone with the sweet stop where the hand touch you can kill someone off the top of the screen with 90 damage. It is advice to learn how to do the dash cancel upsmash as it's a great approach method that's hard to shield grab and is great for surprising campers or people in general.
The down smash though might not be as powerful as the upsmash but is what you will most likely be using the most as it's almost impossible to side step and does good damage and knock back.
The Fsmash does have its uses but is fairly complex, to learn more about it read my thread "Thoughts and Results on Sheik forward smash testing"
Sheik ^B is now a killing move and can be used offensively if your daring enough on platforms levels such as battle field, it also has a special feature that if you free fall for a fix amount of time you can land with no lag or the normal landing animation.
To learn more on this check my threads
^B information
and
More ^B information ^-^
Sheik best approaches are most likely the dash cancel up smash and retreating fairs but she has many other lesser options.
Sheik grab game is one of the only grabs in the game that can reliable set people up to follow up in all throwing directions, however because of Brawl physicals it’s best to chase them in the air with a fair to make them air dodge and then follow it up with either a Nair or Bair with fast falling.
..Oh and it's a good idea to check Ankoku guide.