It's really allways the same. People don't read the missions and say the game is broken.
now i collected few of them all 3 stars all equipped...help
You're going to need to share more pictures, showing the champs who you think qualify for this.
Keep in mind that we get these kind of questions a LOT and in nearly all cases, people overlooked or misunderstood one of the requirements. It's rarely the game's fault.
None of the pics you posted shows you fullfilled the requirements of the quest.
You used attack champs, that is indeed needed to do the quest. You showed us that these attack champs have boots, gloves and chests of the attack set. That is NOT the quest. The set doesn't matter, it could be items from any set.
The quest is to equip items with % atk as mainstat.