Going by this I'm going to guess at a top 3 main of:
ADTR, NFG, The Used in the UK
Alkaline Trio, Electric Callboy and Neck Deep to headline stages. Much less risky than The Used with their form.
No point in entertaining any of these Europeans one's though.
Bit different, QOTSA have been on the festival scene for over 20 years.
It's perhaps more of a case off how festival lineups have fallen. Rather than about QOTSA or Fender.
I like both, like both live. Would I buy a day festival ticket for either, no.
I'm saying more when they are booked, they aren't ridiculous to be subbing, Primavera is also much cheaper. After listening them all I actually think I'd watch Sabrina who I don't particularly take to an Chappell over Chari.