During discussions on recent iCloud issues, it turned out that important role plays submitting requests via Feedback Assistant tool. Usually, you might want to highlight the issue using Twitter, or try using DTS request on your paid Apple Developer program.
Several developers share their experience contacting Apple development teams using various channels.
Apple: Feedback Assistant
Reference: Getting Feedback to Apple
Developer:Submit bug reports via Feedback Assistant tool.
QA engineer:Submit bug reports via Feedback Assistant tool.
PM/DM:Business as usual.