I think they did so many things right with Web Api 2.0 and SignalR. I think there is the possibility in the future where you can take only the parts of the framework you want, maybe ASP.NET vNext.

Again in a lot of ways though those are a response to Node.js and socket.io

All of your points stand: how expensive it is, the fact that it is a bit heavy, and not homogeneous.

I still think it will evolve and will not fall behind like Java etc. but it does not hurt to hedge a bit and start learning the "MEAN" stack :-)