Sheilda (Zelda and Sheik together) is actually one spot above Sheik on the tier list already. But avoiding final smashes is completely irrelevant to a tier list, because it's based on 1v1, neutral(ish) stage list, no items, and the current one is based on the 3-stock 8 minute rule (some say that with 1-stock rules, Squirtle, Ivysaur, or Charizard may be more viable, so that might alter the tier list slightly). Din's Fire is VERY easy to avoid, at best it can harass horrific recoveries like Link and Ganondorf's, but it has upward knockback, so they don't even have a reason to try dodging it while below the stage until like 200+%, and it may actually help them recover (they can just airdodge if it is used while they're high up). it's very punishable if used when someone isn't recovering because one can roll, spotdodge, or [in the case of fast characters] run through it, shielding if you set it off early. Her recovery has some angling issues, and she's got a bad second jump. One can SDI upsmash (and fsmash) to escape it, meaning that it won't actually do full damage or the final hit if someone SDIs properly. She's also rather light.
She MAY be above Jigglypuff (which is a tough argument) but she's certainly bottom tier and she's not better than Link or Captain Falcon. She's better in doubles though, where her high-knockback fair/bair are easier to land, her moveset is safer, and her weaknesses are less exploitable.
Hope this explains it some to you.
