First, some references for further reading, since many of the questions have already been discussed: Opening pack bug in Merecenaries - #5 by SparkyElf-2852, 24.4 Known Issues - #36 by SparkyElf-2852 .
Yes, apparently, that’s it.
Nothing strange about it, and it happens from time to time.
Actually, you should have recevied the basic card from the shop and the golden portrait from the achievement, the former being a known issue, but no matter.
PS
First, in terms of duplicate protection — apparently, not, as stated in the references. Second, don’t most ordinary portrait bundles offer the base version (or rather ‘base portrait’, as it is worded in their description right now) of the mercenary first if it is not owned? That’s definitely the case for those present in the shop for me right now, and others of the kind have worked similarly, if memory serves, the notable exception only being the bundles with diamond portraits offered before the launch of the game — and perhaps something else, which I don’t recall.