I agree, I missed it back in ICC when you'd take a wide menagerie of classes so you can get all the buffs. Spell Haste, Melee Haste, Crit, Stamina, etc.... where you'd move people around to bring in a Shaman or a druid to get a specific ability. We'd recruit Unholy Dk or Boomkin's back in wrath, so they can provide the elemental buff so Warlocks could use others curses.