I used to work in this space. If the DOJ breaks up live nation the only group who gets screwed is the consumer. The sort of artist who is big enough to use live nation also wants a pay day for going on tour. They want the door, they want to sell their merch, they want a cut of the 20$ beer you buy. There might be 1 or 2 artist left who dont want to see you gouged on the ticket but that might not even be true any more…
This is true, of course, but the rest of your claims are pretty speculative. Big bands were touring long before the TicketMaster monopoly became a thing.
A competitive marketplace benefits both suppliers (ie: the bands) as well as consumers. Why wouldn't a band want to play several ticketing companies off against each other to see who can offer them the best deal? It's also not in a band's best interest to rip off their own fans: they want to keep tickets cheap enough to make sure that the stadiums get filled.
In Europe there is a much more competitive market in the ticketing/events space, where LiveNation/Ticketmaster competes against multiple big players like Eventim, AXS, See Tickets, as well as innumerable secondary and resale-market ticketing companies like Viagogo/Stubhub, DICE, Ticketswap, etc. And there's certainly no shortage of big bands on tour.