TL;DR AT THE BOTTOM.

There's a lot of potential for getting rid of minor frustrations in the game, so I want to list a few QoL (Quality of Life) things I've noticed that are in dire need of attention. Feel free to join in and add to the list about ones I've forgotten.

Filtering Champions: 

Champions should be filterable by many attributes, not just sorted or anything like that. The filters should only show the champion that meets the criteria similar to the artifact filtering system. You should be able to filter by rarity, faction, rank, eligible (as in eligible for levelling, ranking, skill books, masteries, etc, instead of searching for the red dots), champion tags, possibly more. They should be available in every place such as team setup, champion choice in battles, etc.

Champion Tags:

To help with organization, champion tags should be visible everywhere. It's like they started to work on this feature and never finished it. Am I the only one using it? Currently they show up in champions list, Vault, Tavern, Sparring Pits, battle champ lists, etc, but not in multi-battle champ queue, fusion menu (especially important to make sure you don't fuse your duplicate you are keeping), I feel like there were more but I can't think of them at the moment. Also, can we get more useful types like fusion, dupe system champ, etc.? Maybe it would be best if we could make a bunch of customs and choose an appropriate icon similar to the I, II, III, but more? I've also had a lot of bugs where they are disappearing or applying the wrong tag. When I pick a heart, it will sometimes apply the speed boot or something.

Artifact Filter Improvement:

Artifacts filter can be improved substantially. Just like the champion filter described above, we should be able to filter artifacts and accessories by rarity and rank. During sell you should have a select all toggle to make selling junk easy. After turning off the filters, keep the sets in the same closed/open status you had them in prior.

List improvement:

This one simple and short. Make it so that lists don't scroll to top (or back to the left) when switching or going back. This works great in tag team and partially in the Tavern, but nowhere else. When you switch from upgrade level to upgrade skills and the other tabs, it goes all the way back to the top. This especially make it frustrating to level and rank commons and uncommons to use for food.

Team Setup Improvements: 

I feel like it must've been overlooked for some reason, but you need to be able to move champs in order when adding/removing from the team. It would be helpful if champs skills had boss or mob target toggle (mostly for ninja in spider, but possibly also for others in other areas like Ice Golem i.e. Heartseaker only on boss).

Sorting (Champions and Artifacts): 

Reverse sort could be helpful for ranking up commons and uncommons for food easily or getting to dwaves and shadowkin faster. This could be rendered unnecessary, however, if you have champ filtering done correctly.

Champion Names could be sorted alphabetically, same with artifact sets or accessory factions. They're pretty random at this point, but I'm figuring localization has a lot to do with that. Champions appear to be based on their faction's order in the index at least.

Lastly, not necessarily QoL, but it would be nice. Give us a very rare drop for a few fragments for past fragment champions in something like clan boss loot, weekly arena loots, or something else. We all realize you paywall them behind summon rushes and champion chases, but if a player went to a whole bunch of effort to get 95 and can't get that last 5 without dropping cash they may or may not have, then they'll never want to put any effort into future fragments.... unless there was a small chance that if you continue to play the game you can get those last pieces.

TL;DR: In conclusion, here's a quick list of QoL improvements that need to be done:

 - Champion filtering by various attributes

 - Improve Champion Tags to be visible everywhere and have more options

 - Artifaction filtering by rank and rarity, more...

 - Lists should stop scrolling to top when going back or changing tabs

 - Team setup needs to allow you to move champs in order. There should be an option to tell champs to target minions or bosses

 - Sorting in all areas could be improved with alphabetical and reverse sort.

 - Small chance of random champ fragments from past events in CB and Arena loot boxes