Fixed in v1.2 (just shipped). You were right - the upper strata flew by too fast to ever roll their legendary. Two changes: legendary odds are up, and there's now a "last find of the stratum" safety - leave a layer you actually dug through and its missing legendary turns up on the way out. Every strata's set should be completable in one pass now, top to bottom. If you go for the full collection again I'd really like to hear whether the upper layers finally fill in. Thanks for the sharp catch.