Start by picking 5 Blizz characters you want to see. If you absolutely must pick more do it in separate posts pleez
1) Deathwing (human form)
We only got to see him in WoW in some gimmick joke quest in the badlands. Seeing him clash against the Lich King; his fiery mace vs Frostmourne, would just be too damn epic. Cataclysm did not do Deathwing justice, at all.
2) Mimiron (in 'voltron')
He would make a great tinker type of class for this game, with the 3 different parts he could have great diversity in weapons. Plus I just like Mimiron.
3) The Lost Vikings (all one unit)
I think it would be neat to have a unit similar to Ice Climbers in Super Smash Bros. Plus nostalgia. Plus SNES.
4) Anduin Lothar (warcraft II)
Warcraft II was my favourite in the series, and Lothar was my favourite character in that game. To me he's the ultimate Paladin.
5) Gul'dan (warcraft I)
The first Orcish warlock and founder of the Orcish Horde, master of the Shadow Council and the creator of Death Knights. What more do I need to add? He's otherwise known as "Darkness Incarnate"... So yeahh good luck with that.