What is the weak point on the Promethean Watcher?
I find the Crawlers pretty easy to headshot, and the Knights seem to at least take a lot of damage if not one hit when their shields are down, if aiming at the head. The Watchers don't exactly seem to have a head, and focusing on the center "head thing" doesn't seem to improve the take down time. I'm finding them super hard to eliminate, and they often overwhelm me. Do they have a weak spot like other enemies?
Watchers do have a head. It's really small and just above the circular light on the chest. The Halopedia has a good close up of what they look like. I've been playing on a 1080p 42" screen and didn't know they even had heads or legs until I looked them up on the wiki. I've had Watchers go down after one or two well placed hits on occasion, so it just may be that the target is really hard to hit given its small size and their mobility.
One tip I can give is that, they usually fold up their wings and fly off when they are one shot from death. This is when you need to make sure and score another hit, or else they seem to come back in a few seconds at full health.