RE: the Swordmage and the new feats, yes, they are a defender class, but at the same time the game's other defenders can get away with taking only one feat to increase their damage. In other words, it's not an intended "defender tax." I think this is a case of design happening quickly, and no one thinking about the specific implications in some of the lesser developed character classes. As I play a Swordmage, I can tell you that they are not one of the heaviest supported classes (at least not anymore).
I think we'll see a lot of minor fixes for issues like this one in the next few months... I'm sure there will be a feat that sword mages can take to get dual bonuses now that the community has noticed it.
And that's the major problem I see with Essentials: now that it's here, there are some major (and a lot of minor) revisions coming at us, and they really haven't been sufficiently playtested. By that I mean playested outside of the in-house group at WotC.
One of the things touted with the DDI was that we would be getting playtest versions of classes that were coming to us. I'd say that if the major rule changes and new classes for Essentials were previewed, many rules compatibility issues would have been discovered before it was launched.
It will be interesting to see how many more issues like this are discovered.
--Steve