A local Timber Framer uses Eastern Hemlock extensively and was quite suprised when I mentioned to them that I had heard of
Hemlock's reputation for rot. He claims that he has no trouble with rot whatsoever, even in some unprotected "doll house" frames.

By the way, the rumours or rot I have heard all eminate from the notorious little hamlet of Alstead, NH. Associated with one of the rumours was the comment that in at least one case the enclosure system employed was a suspect infill system. Early "learning experience" in such a fertile timber framing petri dish as Alstead could very well proliferate to the point of legend. I would be very interested to hear of other more fact based evidence.

Regarding ring shakes, this particular framer carefully plans any affected areas on the timber to be placed in concealed areas such as closets, or dropped ceilings, and of course they don't use these pieces where the timbers structural capacity seems to be compromised. They also apply a finish to the timber in the shop prior to delivery, which I believe should inhibit further "shaking".

I only report what I have heard, not having any direct experience with this subject.