I hear what you're saying. I personally never had a problem with how things worked before the introduction of the stash and the unclaimed tab... but then, when it was the way it used to be I didn't feel inclined to spend actual money on the chests. (We also had quest mode, giving us other ways of getting gold of course) Now that the purchase of chest actually gives you instant access to the cards contained therein, this bug really is completely inexcusable; it's literally taking items away that some people spent actual cash on. This happened to me quite a few times without me even noticing. It also happened with cards I would have happily just sold off. Some people might keep a thorough record of what they lost (making it easier for those items to be re-added) but I didn't, and to be fair I shouldn't have to. If people are reviewing the game negatively because of this, those reviews are well deserved.
While we're at it, you've also brought up another problem with how things currently work with regards to chests. Since chest cards are added to your collection, the more chests you acquire, the more of certain cards you'll have in your collection. We *used* to be able to prune our collections somewhat of unwanted cards by selling them off. We no longer have that option. So yes, we're more likely to see certain cards from chests appearing randomly as we play a scenario; but that's also decreasing the chances of coming across certain non-chest cards (at least some of which are quite sought after). I can't check at the moment, since my game keeps crashing every time I reach the main menu since the new update, but if I could I'm sure I'd find a huge overabundance of cards I don't particularly want in my collection. When I go a-farming, I get pretty sick of finding frost slingshots and slightly better versions of leather armor since my collections has so many of these I can't seem to purge.