Tbh, if any more than two people are being tickled at once, it loses enjoyment for me. One person tickling two can work - Tickle Abuse and UK Tickling had some good videos like that. Notably, in both videos, the ticklees were wrapped/mummified together.
If it's any more than two people being tickled on once, it can become just a jumble of laughs all at once, which actually isn't that audibly nice to hear/watch. Plus, you can only tickle two people at once anyway, but even if you move between tickling more than two people in a video there's too much going on.
I prefer the opposite scenario, where 4 people gang-tickle one person.