Been doing a LOT of open water swimming, and sighting has sorted itself out with the mindful repetition. It doesn't seem to matter much whether I sight before or after breathing.
I think the biggest help for me was the advice to get your head back down right away, even before you realize what you saw. Then as you continue swimming, you can process the "snapshot" you took and adjust as needed. The interruption to the stroke is quite minimal that way.
Funny, I find I'm swimming much straighter in open water than I used to. Part of that might be improved technique or stroke symmetry, but the excellent visibility of the water (100' visibility is pretty standard) helps a lot. I can "track" my progress along the bottom even in 30-40' of water. Beats watching lane lines!