I halve all household bills not solely related to me (such as my phone, car expenses, etc.), as they ask what my expenses were. On the same thread, I didn't include my OH's income with mine, if that makes sense (the latter is obvious, of course, but really it's no different to the former). Obviously if you pay 100% of the mortgage yourself, you can't do that, but in my case it's a joint mortgage, from a joint account, with both incomes credited to it.
We also both took out the card, I applied a few weeks later because I was planning to hold off due to an earlier application elsewhere (but I got impatient). No difference in outcome for either, I had one extra hurdle in that I had to provide a copy of my passport, which I found strange in that we'd both been customers before, but I was the only one with an active account (QF transaction).