I've run into this as well and reported it. What is weirder is that if I try to play a Daily Campaign, the full list usually appears. If I go back to ranked, those BGs usually remain selectable as long as I switch over quickly. To make this make more sense here is a real life example... 1) I try to play a ranked match with a BG I call "Super Tanks" but it doesn't appear as a choice and so I don't start a match. 2) I go to the Daily Campaign and see that my Super Tanks BG is selectable. 3) I return to start a ranked match and Super Tanks is now a choice. 4) I start a game and all is fine. It should be mentioned that the deck in question wasn't new nor recently modified so this isn't a case of simply refreshing the list. On multiple occasions I have found that I am only able to play a certain deck if I go out of the ranked lobby first.
It seems to be a problem with split runes that count as more than 1 faction. It sometimes creates a situation where your split deck is not exactly 15/15 as the split runes are counted twice, so you could end up, for example, with a 17/15 deck. The system doesn't seem to allow for any of these types of decks in ranked.
