Obviously, plans changed when the Wrath of the Lich King expansion came along and warlocks got the metamorphosis ability.
No, not like a bard at all, because bards don't use their instruments as weapons or vice-versa, much like paladins don't use their librams to bash people in the head.The class also uses their weapon as instrument to play songs and musical magic.
Like a bard.
Bards most decisively do not use their instruments to physically attack people. Their instruments are used to play music/songs, and their weapons are used to attack, and those are separate items.
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Feel free to make another one, then, if you believe the results would be different this time around.