I've been experiencing this issue with the Psion Flayers in the Dust Palace on the Heroic Strike Playlist not counting as Ultras when I use the Three of Coins. I pop a ToC, defeat all three Flayers, nothing drops, and the ToC icon still displays as active in my menu. It doesn't get used up. The ToC works for me with most other Ultra bosses. Note though, I asked about it in the forums, and some people experience this issue but others also don't. Thanks!