Okay, I went ahead and tested the following pieces of WetFire tinder:
Test 1) Piece of tinder that was included new in the StrikeForce firesteel handle. This piece had degraded (completely crumbled) in the handle and had started to flake off with an obvious hole in the end seam of the foil packet.
This piece failed to light with the StrikeForce firesteel. I was able to get it to light with a lighter. It burned for the least amount of time.
Test 2) Piece of tinder that was originally from bulk WetFire packaging and had been inside my Aloksak survival kit for a few months. Piece was mostly solid with minor crumbling and flaking. This piece had an obvious hole in the end seam of the foil packet and had started leaving small shavings inside the Aloksak.
This piece failed to light with a Doan firesteel. I was able to get it to light with a lighter. It burned for a medium amount of time.
Test 3) Piece of new tinder pulled out of storage with other WetFire tinder, exposed to no adverse storage or use. Upon closer examination it was easy to see that the end seam had failed on this foil packet as well. Piece was solid with no crumbling.
This piece was able to be lit by the Doan firesteel after breaking into chunks and burned much longer than the other two tests.
Conclusion) There seems to be a problem with the end seams on the WetFire tinder foil packaging.
(I have additional pictures from the tests if needed.)