These were all very highly rated at first, though by the mid '90s, Baywatch's ratings had cooled down, and by the late '90s, its ratings had declined considerably.(at the time, TNG, Baywatch, and DS9 was the holy trinity for these shows. TNG went off with a well respected run.
Trying to? Xena did! Hercules did too! DS9 was #1 in first-run syndicated action/dramas for a few seasons, then Hercules rose up and managed to take the top spot, the Xena. Xena held the top spot for a few years, though it wasn't #1 every week. In the late '90s, the order most weeks was Xena #1 Hercules usually #2 DS9 usually #3.and DS9 found itself with TONS of syndication shows, Stuff like Xena even if it was fantasy was still trying to dislodge DS9 as a top dog syndication.
It's weird to think of Hercules having more a following than DS9, but one has to remember at the time, the fantasy genre's revival was new. All viewers had before 1995 was 2 Conan movies & Red Sonja (and the 64 episode Conan the Adventurer cartoon if you were a kid. That one's usually overlooked compared to Transformers and the like, but it was on a Thundercats level of quality. Don't ask me what happened to episode 65). It was stunning, the terrain (New Zealand) looked unlike anything else on tv then, and here was a series with monsters, warlords, Greek gods and the like. Those shows really took off in the 96-97 season when they developed a gallery of recurring characters (like Ares, Aphrodite, Autolycus [Bruce Campbell], Joxer, all had just 1 app. the previous season), though their ratings were great earlier on too. For fans of the genre (especially kids/teens who had played Zelda games or RPGs), it was the 1st tv show they saw in that setting. It was like the Lord of the Rings trilogy for genre fans before Lord of the Rings was made.
WB was the other channel. I'm not sure about DS9 being forced into odd hours. Even with the programming glut (the huge number of shows available around 1996 & 1997) and the expanded networks, there still was some choice syndicated slots available and even on its worst week*, DS9 was still the 3rd highest rated syndicated show out there. A channel putting Xena, Hercules, or DS9 into an overnight timeslot would be shooting itself in the foot (unless it were a network channel [any but WB, UPN] in a small market with no real indy station). In my area, those 3 shows and a 4th show (Sinbad, then Earth: Final Conflict) were on Saturday afternoons in a 4-hour block. It was wonderful. And during most of its run, DS9 was #1 or #2. If a channel had all 3 shows and had few good timeslots for syndication, obviously those are the shows you put in those slots. Shows like Nightman, Viper, Outer Limits, Poltergeist: The Legacy, Mortal Kombat: Conquest, were given crappier timeslots. Oh, and EFC's ratings didn't even compare to DS9. Its ratings didn't even come close to Herc or Xena even at their worst.Then when UPN and the other channel (think it was called CW) came on board, it was basically a block package of syndication. Voyager was the lynch-pin for UPN. This forced DS9 into all sorts of odd hours, and even a fan would have a hard time finding it. (Not like the internet today where you could look it up when it was showing.)
Not sure about Highlander's ratings, though to run 6 seasons without a consortium like Tribune at its back (ahem, EFC), it had to have at least decent ratings. In my market, it was given Saturday night around 6, 7 or 8 (I forget when). Saturday was the network's weakest night, which is why they abandoned it except for filler content or reruns after 2000. From what I've seen, the best timeframes for syndication were around noon to the 10PM hour or so on Saturdays. UPN & WB gobbled up most of the days of the week, preventing counterprogramming against the network's schedule (AKA finding the weakest nights or hours for the networks and presenting a show whose audience wouldn't be watching its competitor shows at that time). But many syndicated shows just felt like they belonged on Saturdays (or at least the weekend). The syndicated set of shows felt like the successor to the kung fu and monster movies of Saturdays in the '70s/80s.
*: except for 4/14/97. Not sure what happened that week. Maybe it was omitted from the ratings listing?