not really, there's a pretty clear path to the creation of the heros in WC3... C&C had unique hero characters that the player either had to keep alive or use to compelte a mission. SC did the same. WC3 then made them upgrade-able.
C&C introduced units that gained experience, blizzard took that idea as well.
Dune 2, released in 1992 had three distinct factions.
Again, blizzard doesn't try to reinvent the wheel, they just make it better.