I think that the economic difficulty badly needs a slider to cater for everybodies individual preferences.
I've tallied up the posts in this thread and there are six people (taltamir, jscott, spacecadet, joseph, titanwarrior, fishman) who like things as they are (beta 4).
There are eight people (eisenhammer, darkwraith, ashberry, munchies, das123, interesting, lancer, alexaexuk) who think it's too easy.
Another two expressed a need for a difficulty slider without coming down on either side.
So even in this small sample you've got a 6 to 8 difference of opinion with the balance saying it's too easy.
I don't think that you can afford to let this issue simmer and stew.
Most people interested in 4X space games would have experience with at least one other example of the genre. I can't think of any that don't have difficulty settings. People are used to having that option.
Aiming for a default middle ground is like chasing mirages. The problem is that you are going to have a significant percentage of your user base thinking (and saying) that you've made the game too easy.
DW is a game that is largely marketed (from what I've gathered so far) by gamers word of mouth and posts on other forums. The last thing you want is people posting that the game has been 'dumbed down' or 'nerfed' to cater for the RTS crowd (not saying that's the case but whenever you have a lot of people saying the game is too easy then you leave yourself open for this kind of stuff).
Potential buyers are willing to give a game that errs on the side of challenging a go but having a reputation as an 'easy' game without the option for choosing your preference is a bad look. Word gets around and even if you instigate a patch with the aforementioned slider a couple of months down the track you've having to make up a lot of ground. You've probably ended up losing a bunch of sales in the initial launch period when the game is fresh and new.
The previous paragraph is me with my 'game business' hat on. It's a pretty raggedy *ssed hat so take it with a grain of salt.
I'd stress that I'm not advocating making the game harder to cater for my personal preference here. It's important to cater for both groups. I am putting a case forward that you implement a difficulty slider as a matter of priority.
Personally if I can't get a challenge out of a game then I lose interest in it pretty quick, no matter how good it is. I suspect that there are a lot of other 4X players with similiar views. I've found ways with DW (as posted above) how to maintain the challenge so I keep playing it an enjoying but others may not bother to go to the extremes that I have.
I think DW is a great game with a great future. But I can see that you are going to get hit pretty hard if you let this issue blow in the breeze for too long. There is nothing in this post that you probably don't know or are aware of but given that you've already summoned the 'difficulty monster' out of the depths and had him zig zag across perceptions, I don't think you can simply ask people to ignore him with reassurance that you'll slay him some time in the future.
Of course all this is a personal opinion and I've been known to be wrong. Numerous times.