Many, many times I’ve had maxed heroes but special at 4 or 5. Then I used feeders to max special, with odds up to 80% or 90%, but it has failed many, many times. But MANY. Now I only level up to 100% or I don’t try
Maybe my imagination but it sure seems like they nerfed the chance to level the special skills. I never had an issue previously but haven’t seen a special increase for weeks.
I’ve felt the same. In the beginning, I could get my 4* and even sometimes my 3* at 8/8 before getting to max level. Now it’s very hard to do that.
I’ve had better luck at getting a special level up when leveling up to an ascension by feeding 10 when less than 10 are needed to hit max.
Level up the special by “overfeeding” then hit Ascend and get another special level up. Get the points to where one 1* will hit max then feed 10.