I played her extensively earlier this week for the express purpose of making sure she got proper placement on this list.
On paper she’s absolutely competitive and her spread reduction was a lovely buff. But the meta has been massively oppressive to Bio DPS and unlike Mauler, Odachi, or Artemis, Cinder doesn’t really have a method for dunking early in the match. She has to build her stacks and by the time she’s ready to go HAM with Acid Bomb and ridiculous weapon damage, she has often has to deal with a Flatline being protected by 1 or more shields. My Cinder is 12.8k power, a Defender Shield from a 12.8k Butter takes roughly 800,000 damage for me to clear off Flatline. It just doesn’t work when the other Godly/Competitive DPS will have shredded your support in the meantime.
Also keep in mind that unlike Ronin, her weapon bonus is elemental, which is a big problem with so many energy heroes around.
Edit: Even in the elemental brawl it was a big problem that Cinder had to wait for stacks to begin doing serious damage, everyone is trying to kill a hero in the first 20 seconds and Cinder really struggles to play catch-up.