I play really good DKs regularly lol
Don't run into his shield aggressively. Needles are your friend in this matchup, so don't be afraid to retreat for some distance and camp with needles. Projectiles will really annoy the DK especially if he doesn't have platforms to use in his approach. He can't close the distance quickly once you start sending needles his way regularly so you should be able to get some openings and damage this way.
In my experience it helps to maintain distance this way for the most part and have him get used to this pacing. Once you see a decent opening, say perhaps if the DK decides to use bair approaches and is rather close to you as is, u can go in with a shield dash. You need to work on getting that grab on him. After the grab, dthrow, fthrow, bthrow all work well. Once thrown and in the air, don't get hasty and cautiously approach. If he airdodges, WIN. Start the juggling, perhaps with another grab or ftilt at low %.
First time you put him in ftilt lock I suggest you keep it as long as you can and see if he UpB's out of it, which he can. Most good DKs with Sheik experience will know this. A lot, surprisingly, don't If he doesn't, grats the match has become that much easier. If he in fact does UpB out of your ftilt lock, he's gonna shoot for one of the edges so he can have a safe landing by grabbing the edge., so run after him on the ground and intercept his landing with ftilt. If you caught him, this can very well end in a gimp:
The Swam Combo works very well on DK. His aerials aren't fast enough to escape, so his only real option is upB, which just resets the situation. If you caught him with ftilt on the edge, repeat maybe 1-2 more ftilts until u got him high enough so you can then sh fair. Since he's off the edge now and fair hit him downward, you can usually walk off the edge with an fair, then sh fair him again and then recover with vanish or chain. I recommend chain if you can, so you can keep yourself hanging. Depending on % and DI, the DK may have been sent too low to recover at this point so his upB will just get to the stage but be too low to get above, and your chain will hog the edge.
IF this gimp becomes a possibility, as in the setup are made, go for it as this is the earliest you're gonna kill DK. He is pretty much the heaviest class in the game so simple power KO's with Sheik won't go so smoothly. In fact in this match-up I use usmash to damage, not KO, since killing DK upards won't happen until 150% or so anyway. I prefer hitting him off sides and intercepting. Usmash also has that special double-hitbox if timed right to do 30% damage.
When offstage and recovering, watch DK's upB.. it has good priority, ESPECIALLY the beginning of it... which also has good knockback and can gimp you when you try to gimp him. Sheik's aerials do indeed hit DK out of his upB, but requires specific timing and spacing and it's risky.
So, to sum it all up:
- Play campy with needles as much as you can -> pressure and damage DK, while also preventing him from building up his momentum or setting the pace
- Look for openings to rush in with a shield and grab.
- Once you get control, keep him in the air with his front facing you, and juggle him as much as you can. Test for upB escape. If he escapes, follow.
- Go for swan combo, especially near edge to continue off stage for a gimp.
- If DK ever regains neutral grounding versus you, retreat and camp needles.
PS. The DK may get angry at your needle camping, since it will most definitely irritate him. Keep in mind though, that this is a necessary tactic as Sheik vs DK, as he can kill you no sweat under 100% while you have to get him to 150% or so minimum on average to get a clean KO. You have projectiles, he doesn't. Use them. xD
I think that covers up everything... although I think I got ahead of myself and posted an entire essay.
EDIT: Oh Oh Oh! If he EVER gets you in his cargo hold, usually meaning he wants to stage spike you, don;t mash buttons. Simply hold the control stick up. Holding the control stick up when DK has you in cargo hold provides the same input as mashing buttons perfectly. This will ensure you get out of his cargo hold as fast as possible.
