I hope at least 14 bosses or more will be in the raid.
What kinds and groups?
I'd be happy to see a raid that would remind of Dante's Inferno. Gates of hell and circles going down and down below. And some big deformed demons unseen before because they are too big and slow or agressive to their own kind as well to be used as legion troops through the portals, but are strong enough to protect Mac'Aree's main place - the great portal through which Sargeras can arrive from the Nether.
1. Familiar names: Magtheridon (first or one of the first), Hakkar the Houndmaster (skeletal knight with a whip of course), Varimathras (as member of the nathrezim council certainly along with others like Mal'ganis, Detheroc etc), Malchezaar and Jaraxxus (eredar not tweens), Talgath (likely he was KJ's vice president so he'll be endboss of the upper line of the palace, KJ's throne, before we go down through the "Stix" to "Dis" ).Maybe Aggonar, too.
2. Strongest demons of their kin: the Grand Inquistior (would reeealy want to see one), aranasi queen, biggest Mo'arg or Fel Lord, doom lord chieftain, the Succubus Mistress (really want this one cause encounter themen on seduction, temptation and "forbidden love" would be something fresh imo), Mother of the Impkind, because we need that too.
3. Mechanical: some soul engine, forge etc, some demonic cannons, airships, fel reavers, whatever. With adds, like the Blast Furnace, but with souls and fel. Abyssals too.
4. The corrupted ones. Different races and creatures, some captured and tortured from the Army of the Light. This might be a wing that would end with the Grand Inquisitor.
5. I really really hope to see at least a couple unique demons that have no kinds, single in existence. Biblical references of the Beelzebub, Belial, Vaal (or Baal), Moloch, Abaddon, Azazel etc.
So I'd like to see a raid that would be reminiscent of Dante's Hell and Armageddon at the same time. Any other ideas?