The entire UX outside of matches is fairly poor. The VS screen layout is unnecessarily similar to the Collection layout even beyond the Edit/Delete buttons. The fact that it's easy to confuse the two at a quick glance is poor UX.
Play should be a drill down menu, where you need to click Play and then for match type and then choose decks at a sortable deck selection screen, in that order. No choosing a deck without confirming match type beforehand. The Edit button should be removed as well; too much duplication of functionality.
Collection should have sortable (not just filterable) card/deck screens, and "New" marks on cards so you know what you got from recent chests. The Import Deck and New Deck buttons are very strangely not placed next to each other despite their similar functions. The deck builder should be more similar to online deck builders, letting you add cards you don't own. It's also way past time Riot fixes the bug where clicking the area next to "Done" ...