One more idea to deal with Dillution

Jacklag

As most board users have heard by now, the game is suffering from an excess of characters, specially 4* tier, but also somewhat in 5* tier as well, a problem which only grows every 2 weeks with the release of one more character. While champing a new 4* is relatively easy, for a new player to collect the old ones is not only difficult but also kinda useless outside of very specific conditions. Usually the character will be useful for one event and then return to obscurity.

So here is an idea. Special Stores, lots of special stores. First, get rid of the Classic Legends store. Replace it with a cycling store that gives out 3 to 5 classic 5*s each week and, say, 16 to 20 4*s. IDK, you guys do the math. This store could change once per week, allowing players to pick a time to spend their rewards and, while still randomly, get more of the rewards they seek.

And allow players to spend their Legendary Tokens on this store, instead of only on the Latest Legend store. Another thing that could come more often would be Thematic Stores. Much like the Anniversary Store that features the 3 most popular 5*s and a higher chance of getting the most popular 4*s, I would recommend frequently (maybe by-weekly) releasing stores of 3 5*s and ONLY 4*s that fit the theme. Like, for example, SPACE ODISEY, featuring Silver Surfer, 5*Thanos and Beta Ray Bill plus all the 4* Guardians of the Galaxy, Carol Danvers, Thanos, Nebula, and so on. SUMMERS LOVING, featuring 5*s Phoenix, Cable and Havok plus 4*s Cyclops, Jean Grey, Emma Frost, and a few other X-Men. KINGS AND QUEENS, featuring 5*s God Emperor Doom, Black Panther and Black Bolt plus 4*s Medusa, Lockjaw, Kingpin, Emma Frost, Shuri and so on. I think this could be really fun. 

All that in addition to reworking some of the old 5 and 4 stars to make them useful again, which I hope you are working on already.

Cheerios!