So are tribute characters.
You'd be wise to separate the wheat from the chaff.
None of them are Rock N' roll or heavy metal. You know why? because it doesn't belong to any of the races' cultures.So is music. Kodoriders have been in WC3 as support units that play music for buffs. They're effectively the Horde variant of a Bard.
Most of the Aura items in WC3 came in the form of instruments. Scourge Bone-Chimes, Lionhorn of Stormwind, Warsong Battle Drums, Legion Doom-Horn, Ancient Janngo of Endurance, Alleria's Flute of Accuracy. From these items alone, there is enough material to form the basis for an actual Bard class.
Leatherworking even carries some of that theme over with the Drum kits that give Bloodlust.
What's next? techno and trance for Bards? come on.. you'd have to adjust the class for everyone's taste in music.Heavy Metal and Rock can simply be flavoured abilities. It doesn't have to seep into every aspect of a playable Bard. As I explained to Teriz, you could literally take one or two ETC talents from HOTS and insert them as Bard Talents, and that would be enough to allow you to fulfill a Heavy Metal flavour for your Bard if you choose to, while 90% of the Bard itself would be built around more standard class mechanics. It's the same as Monks having all things Alchohol related being exclusive to Brewmasters, and even then it only really appears in one or two abilities through the entire spec.
There's nothing out of place in the Brewmaster's alcohholic themes. It's, literally, an ancient custom as time itself.