I know lots of people are getting frustrated with token pull rates, rotated out characters, etc so I came up with a solution that I think would work for just about everyone; including D3. So here it goes.
There are currently 7 
, 14
, 31
, and 5
characters (including Rocket & Groot and Gamora). Using Heroic tokens as our baseline, you are about 7 times more likely to get a
(12 @ 6.3%, 1 @ 4.2% or 2.1%/cover) character than you are a
(20 @ 0.9%) or
(3 @ 1.0%) character. Also,
characters make up about 80% of the total distribution. That said, here is my proposed change:
Standard Tokens: Give only
and
covers.
Heroic Tokens: Give only
and
characters that are NOT featured in the currently running PVP, PVE, and LIghtning Round events for each week.
PVE Tokens: Same as Heroic, but also give PVE featured character(s) of all rarities at an increased drop rate.
PVP tokens: Same as Heroic, but also give PVP featured character(s) of all rarities at increased drop rate.
LR Tokens: Same as Heroic, but also give LR featured character(s) of all rarities at increased drop rate.
This should ease the diminishing pull rate % for covers for a bit and allow for more room to grow for the devs without rotating out any characters. It may require some change to progression rewards as well, but overall I think it’s a better solution.
Edit: I was going to get in to a long analysis of what I thought would be good for new drop rate % based on my proposal, but really nobody would care and it was too much work for me to bother since D3 would likely just use their own anyways.