Meh, please tell me of one rts in the past 5 years that had a story worth playing? RTS AI is always flawed because I don't think our currently level of technology can ever provide a smart enough opponent. The last RTS I played through single player was SupCom and this was only cuz I was reeeeally bored. Look at WC3 - I've played it for years, and never in a long time have I either played the single player campaign OR the default game maps.
Multiplayer makes an RTS, single player really isn't worth the extra time and money for development. Personally i'm really glad I can play Demigod right now as a multiplayer game only then have had to wait 6 months longer while they put in a campaign that most people will never play or lose interest in straight away.
+1 to GPG for making this decision.