Sheiks tools for victory are all there but no one has learn to used them all property
Sheik ftilt into usmash
With proper counting sheik has a guaranteed true combo on everyone into killing % usmash. For example if sheik hits another sheik with with a ftilt of the listed decay levels below she will have enough of a frame advantage to use a tipper usmash. These are killing %
1. 77-80
2. 77-87
3. 77-94
This is not just limit to just the first 3 decays as I've seen it going up to 5 decay levels which allowed higher then 100% damage guaranteed combos. Then we got the next broken tool and most likely will effect sheik tier placement more then anything else...The chain.
The jump into chain and even normal can instantly change a match around within mere seconds and it compellingly changes how sheik is capable of fighting. The normal chain if used property can caused a locking like effect for dozens upon dozens of hits within mere seconds. Doing such large amounts of inescapable damage such as 90% within 3 seconds. This as you would imagine is difficult to land since the chain does have some start up but think about this, the chain can't be side step because of it's nearly constant hit box, can't be shielded because it pokes shield extremely well, you can't roll because of the hit box being out, can't jump either so all you have is to attack and if the sheik is moving it fast enough the disjointed hit boxes of the ping proof chain will beat it out...unless your marth.
The biggest sheik changing tool though is the jump into chain, excluding jack chain. The jump into chain gives the chain new properties such as a less active hit box, more hit stun for each hit, and increased damage. Because of the now existent hit stun sheik is capable of effectually keeping someone away with the chain. The most noteworthy of those that she is capable of keeping away are Meta knight and Game and watch both of which are listed to be fairly bad match up's with sheik. With the chain in play and with meta knight having a decent amount of damage on him (like around 50%) sheik is capable of swatting away every approached method meta knight has and can thus force a stalemate if both players have the same % of damage. This can also be done for game and watch but without the need to waiting till such a high % because his attacks take longer then meta knights to come out.
Another noteworthy feature of sheik I'm going to list about the chain is on the edge chain lock. With the chain disjointed hit box and rapid fire attacking she is capable of halting below stage recoveries entirety as she lock her opponent into a free fall of hits. The chain can hit them so fast so much that they will be unable to sweet spot the edge even though they will be mere cms away from it.
Those are a few of the larger things I can see sheik using to raise within the tier list that aren't done normally. Such things as the normal ftilt lock and dacus punishment is very effective but it wont get her out of mid tier
SHEIK FOR HIGH TIER!