I have a pair of 2-3 yr old MLD Rain Mitts that I have also seam sealed.
They are well made, but I found that while gripping my hiking poles, the pressure of gripping the poles pushes water through the fabric of the mitts and my hands get soaked.
Not the fault of the rain mitts, just my style of hiking.
That said, someone from BPL posted a solution to this problem....wearing latex or non latex gloves.
I have worn them inside my MLD Rain Mitts and it seems to do the trick.
I carry the latex gloves as a part of my med kit, so maybe double duty with the latex gloves?
I guess I could try to skip the rain mitts and use the latex gloves, but I think that the rain mitts are providing abrassion protection to the latex gloves to keep them from getting holes in them.
So the combination seems to work for me on the few times I have been in the rain.
Hope this helps.