You do appear to be correct about the RCI buildings simply not living up to the dispatch missions. I was trying to prop up one race by helping them build a bunch of buildings, until I just said "fark it, I'll do it myself". It's super easy with dispatch missions to drive them up (or down).
During my last game, which I completed, I never really felt that the universe was in much danger while I was away on long dispatches. Usually I'd set things up so if anything did happen, it would trend toward my favor anyway. So in this way, the "cost" of dispatch missions (time) isn't really anything to be that concerned about.
I don't really agree with you on the attitude building vs relations dispatch. The relations dispatch is capped isn't it? And horribly expensive. The attitude buildings are a great passive force in getting the relations set the way you want, and they work alongside you when you are dispatching elsewhere.
As to your question, I'm not really sure. I guess I'm kinda indifferent. Either way I'm making use of a game mechanic, I'm more concerned with the balance of pro/con/risk/reward than what flavor it comes in. Take a look at pirate bases. You can either destroy it yourself, which is easy to control (win), and gives you nice rewards. Or, you can ask a race to do it, which costs you something and... can they fail? I dunno, I can't figure out why I'd ever want to do it...
