Sure it fits.
Grom Hellscream in WC2 was metal as fuck.
ETC's members would all fit in any raid, even with their metal inspired instruments. The Arcanite Ripper and Sun Lute were even obtainable weapons that let you turn into ETC members and play rock music. This is as far back as TBC.
Did you never play TBC or get these items? Cuz they were legit epic weapons, not just toys.
Nothing is 'grounded in lore' until it actually enters lore.It actually is, because it's not grounded in lore.
Pandaria wasn't even truly grounded in lore until Mists of Pandaria formally introduced it.
Rock and roll does exist in WoW since ETC and Blight Boar are both canonical.