Quality of Life stuff you'd like to see
Army Troop Equip
What currently happens: When selecting a mini and clicking "Equip" you get a screen that allows you to place that mini in one of the six army slots. You can't see the tags on the mini you've selected in this screen, only the tags in the army slots.
What should happen: Any army slots that would "support" that mini should highlight, so you know where you can put the mini and still get the bonus levels. Example: I select safe pilot. I have Malfurion open. Safe pilot has the tags: Ranged, Elemental, Unbound, AoE. In my Malf deck, my custom slots are Spell/Unbound/Elemental and Wild. His static slots are Cenarion and Alliance. So the Alliance/Wildcard/Unbound/Elemental would all highlight to show that Safe pilot can go there.
Army Upgrades
What currently happens: When clicking "Army Upgrades" and then "Change Upgrades" and selecting an Army slot, you're presented with a row of all the different upgrades you can select from. You can't see the mini you have equipped in that slot though from this screen.
What should happen: Army slots that give a bonus should be highlighted. Example: I have an Elemental slot with Pyromancer. If I wanted to change that army bonus, "Ranged" would also be highlighted because Pyromancer has that tag.
Information under Currency
"Experience" can be thought of as currency in the sense that it's collected and used, and the same thing is true for banked quests. When clicking on the coins drop down, we should be able to see how many quests we have banked (E.g. 25/300). We should also be able to see how much experience we've collected out of the daily maximum (e.g. 24,730 / 50,000).
Both of these things are "hidden" information that leads to players coming to the forums asking "Why can't I do anymore quests?" and "Why am I getting 0 XP?" Just telling players what's going on is often the simplest solution.