This is not to complain, but if you have one account, and you see a certain toon all the time, that doesn't mean someone else is getting the same rates. I have 2 accounts (1 guest and one login). Prior to Bossk, I was farming Dengar in both accounts for a time period. In one of my accounts I have him at 4 star + 14 shards. In the other I have yet to unlock him. Vice versa, same situation with Jyn Erso, 56 shards in one, 5 star +78 in the other.
I'm not promising I've farmed both the exact same, but both were definitely similar. I can't say that I checked both for every single refresh. I probably focus on farming the ones I wasn't making progress with. However, I 100% believe that some of us may get very different results with the same effort/focus.