The more important for the campaign, is the story, for me more lore, more coolest, i'm addict in wow/war lore xD
After the gameplaty, for me, don't need be so uniqueness, one or other must be, for have a difference of blizz campaigns, but all the maps must be fun.
And then come The terrain / skins / models / special effects etc.. this just attract the player, well the terrain enter in the essencial, i'm already don't play some campaigns by the terrain was bad o.o
One thing that ]i learn with tomoraider was; a campaign need emotion; rage, happy and the others, all the facts must be clean for the player, why that happen, or don't happen, why the character die, or survival, hope this could help you, and i wish all the luck for you !