I had hot fence (electrobraid) in MN and an auto water in the fence to serve two fields. No problems with it, but the 6 ish feet around the waterer was wood fencing (the electric went over the waterer in an insulated cable, attached to the wooden fence) and it never really got overly muddy there (but I think we added screenings to prevent.) The waterer itself sat on a concrete pad that was large enough that the horses stood with their front feet on concrete to drink.
The waterer was near the gates out of the field, although they were rarely used to bring horses in/out, as those two fields ran into the sacrifice area via different gates, and that access was generally how we moved horses. Looking at the map, the waterer sat 25 feet in a straight line from each gate, and 20 feet into the field itself. There was also an outlet with easy access which was handy when the very cold temps froze the waterer and I had to thaw it with a heat gun (0 stars, do not ever recommend, probably never an issue unless you’re crazy and move to MN or someplace like that!)
Anyway, no problems with that setup and would happily build it again like that if I had the need. I’d rather spend the $$ mud proofing near a combo gate/waterer area than trenching further for the waterer–you’re likely to need mud proofing at the gate anyway (and probably the waterer, too!) so why trench more + mud proof the gate + mud proof the waterer, when you could trench less and mud proof ONE area?