I still routinely backup and sync my iPhone 6 and my old iPad mini 2 (both are on iOS 11) over wifi to iTunes (latest HS version). Although the process is by far not rock stable, I can confirm it does work most some of the time. Every once in a while iTunes will show me some strange error message saying it could not complete (although sometimes the backup works yet it still displays a warning) or the iPhone will still show a rotating sync icon next morning even though the backup actually completed late the night before (when I plugged it into power).
While it is far from stable or reliable, at least so far my impression has been that when backups and sync have completed without warning, they actually have completed correctly.
I like Adam’s advice to use iCloud backup as a second method. A “backup” for the primary backup plan definitely makes sense. For me personally, iCloud won’t work for that. For one, I don’t want remote Apple servers to hold my personal data and secondly, I could never get it to fit within the 5GB Apple gives me. But I would definitely be interested in some added security that my backups are good. iTunes syncing doesn’t instill much confidence these days.