Oh, I agree it is most likely JLM's DNA on the cigar tip. True, I see your reasoning that the shirt was found prior to MH's remains as a good explanation. However, I am having a hard time believing that there would have been no DNA transfer to her undergarments and her tights/leggings. Not to mention the perp likely carried her to that remote cow pasture, so there would be skin cell transfer as well.
She was exposed to winter elements for three months, and according to a forensic specialist quoted in the source I read said that her clothes would have still been intact after that amount of time and that synthetic fibers like polyester are virtually indestructible; they "last forever". Just seems unlikely that they could find not enough DNA to extract a profile on clothes that he likely had sustained contact with at the time.
I think that the t-shirt is much weaker evidence and am really surprised that LE would not have checked the cigar tip profile with clothes she was wearing instead now instead. At this this stage they could have easily tested for matches on the clothes found with her or the Pantera shirt. Why choose the weakest one in terms of exposure to multiple DNA sources? Further, the tee shirt has a high cotton content to it, and cotton degrades most rapidly of all fibers. It seems they went with the Pantera for some other reason that they will likely have to explain. LE needs more than that Pantera shirt to prove JLM raped and killed MH, IMO.
However, forensic anthropologist Lee Meadows Jantz of the University of Tennessee's so-called "body farm" says that a body discarded for three months would still have its clothing intact– even cotton, though it's the first fabric to degrade. Next in line are silk and leather, but polyester, she says "lasts forever."
-from source at C-ville weekly.
I think perhaps you're forgetting that the Pantera shirt was on that bush less than a day and prior to that it was, most likely, in the possession of JLM for just three weeks, PLUS, it had a blood stain (rich in DNA). So it doesn't matter that the shirt was cotton because it wasn't exposed to the elements and they tested the DNA found in the blood stain. IMO