If you are looking for a campaign based strategy game, King's Bounty and it's sequel are solid choices.
It's my understanding that sandbox was chosen to enhance the replay value. I prefer sandbox but my thoughts aren't the topic of this post. I agree the campaign isn't a campaign. It's really a tutorial of sorts. If I may, I recommend that you give the mod community some time with the tools this game provides. It has been stated many times that you can produce a RPG style game with quests, triggered events, etc. I fully expect the mod community to produce at least a few RPGs.
This. King's Bounty and Fantasy Wars/Elven Legacy are great story-driven, campaign-focused, turn-based strategy games.
And do come back in a few months. Stardock called the campaign that shipped "Book 1" and made no effort to hide the fact that The Story Will Go On. And modders will no doubt go crazy with the ssytem, especially once they start figuring out all the xml and python. Nobody's going to say Elemental's perfect right now just the way it is, but you're doing yourself a disservice to judge it finally based on what you see here. It's designed to stick around for awhile. 
