I use fletchinder in RU and UU where it's pretty great, so I guess I can give an explanation of its general use.
It's really great at sweeping weakened teams because it has the strongest priority move in the tier, wins sucker punch mindgames with WoW and priority roost, and wears down its rock/steel type counters with a wow when they switch-in. Its SR weakness isn't honestly too big of an issue for it given priority recovery and only ever attacking with priority. It can generally scare out more frail threats to find time to SD or roost on them.
I generally run it on HO teams because it seriously fucks over opposing HO teams while still having a use against more balanced teams, but I know people like FLCL have run it on semi-stall to take advantage of its ability to sweep once its checks and counters have been worn down.
I mean you look at the burd and see absolutely terrible stats and typing but it's fine because gale wings is a broken af ability which turns it into a great mon.