How to book a Battle Royal and get a good rating?

You probably did it but make sure to use slow build for matches longer than 16 minutes. 58 sounds really low for including popular workers. You can try to end the show with a angle (maybe the winner celebrating) to get a top rated last segment. Or to make the WW3 the semi-main event and instead finish with a singles match for the World title.

This is pretty much the concept I use:

Reglular matches under 15 minutes
Regular matches over 16 minutes (slow build)
At least one throwaway storyline match
At least some hard-hitting brawl match (like the classic Vader vs. Cactus Jack series)
If I run the Cruiserweight Division I book them 14-15 minutes (All Out)
When I run War Games or Battlebowl Battle Royals I always use slow build

I never use epic, once in a lifetime or the other aims (imo those only ruins the grades).

Just did WW3 PPV in 2002 so a year later literally IRL and in-game and took the advice given here and also what I found on a reddit forum.

So 2001 WW3 my main event WW3 Battle Royal got 68 rating making the overall show raintg 58 - it was the Main Event.

For 2002 WW3 Battle Royal it got a 78 match rating and I used the following to book:
- 'Keep Strong' on all workers involved who have a psychology rating higher than 80
- Slow Build
- Regular
- Decisive win (I had intended to have interference for final elimination but saw some posts say to keep it regular for a good rating.
- I did have 3 interferences during the Battle Royal but not the finish to give some heat to some ongoing feuds
- My roster and popularity are much higher/better than the previous year so probably helped
- Avoided using any occasional wrestlers/legends as they seemed to give me bad ratings in the previous one

Unfortunately I didn't trust these changes would work so I took another posters advice and created an Angle for the Main Event: which was Eddy Guerrero celebrates having just won WW3 - He has average 84 popularity in USA but unfortunately it only did 65 for a rating and unlike the previous WW3 in 2001, I should have kept it for the Main Event. You live and learn.