Hey there, wasn't aware if this was common knowledge (in terms of there being a thread/post) but it looks like bosses will have Illusion drops for old content for our wardrobe.
Warlords of Draenor:
Kargarth Bladefist - Illusion: Mark of the Shattered Hand
Tectus - Illusion: Rockbiter - Shaman only
Kilrogg Deadeye - Illusion: Mark of the Bleeding Hollow
Blackhand - Illusion: Mark of Blackrock
All level 90 requirements and Bind on Pickup.
Mists of Pandaria:
Will of the Emperor - Illusion: Colossus
Sha of Fear - Illusion: Jade Spirit
Cataclysm:
Nefarian's End - Illusion: Power Torrent
Al'Akir - Illusion: Windfury - Shaman only
Wrath of the Lich King:
The Lich King - Illusion: Rune of Razorice - Death Knight only
Burning Crusade:
Nothing.
Classic:
Ragnaros - Illusion: Flametongue - Shamans only.
Just thought i'd share, if it's old news and not needed, please delete.
Thanks.