The lack of communication was exactly the reason behind the offline thing getting so big.
Had FD communicated to the playerbase what's happening with ED's features (big picture, no need to get into details) every few weeks there wouldn't have been an outrage because players would have been already aware of the difficulties and the uncertainty of the feature.
The problem with keeping customers in the dark is that there are going to be surprises. Sometimes that's good but as we saw with offline-mode those surprises can also be extremely bad.
Cut the amount of surprises and you cut the amount of outrage. Also letting people have some info gives the players something to look forward to which is a really good way to keep people playing.
I think the problem with offline was that the decision was made quite late. They probably should have said earlier that it might not make release and could be dropped entirely but to be honest I'm not sure the result would have been much different. Remember when they said "we think we're probably going to have to wipe at the end of Gamma"? The response was rage, debate, demand for certainty, and endless polls about whether they should wipe or not. Same thing would have happened if they had said anything about offline earlier.
If you follow your point about surprises to it's logical conclusion it makes sense that they are not saying much. Only unannounced features can be good surprises so at best a roadmap is blowing all the good surprises at once. But any expectation they build up with a roadmap is a potential bad surprise in waiting. A roadmap that says "we're going to do A, B, C" will be taken to mean that X, Y, and Z have been cancelled, whether that is the case or not, so the outrage will still happen. And if they later decide against A, B, or C then it's offline mode all over again.