How I would fix the Diversity issue in AW
Instead of having Diversity points lets bring back Defender Kills and then give a bonus based on total number of classes as defenders and which ones got the most kills.
Your Tech defenders get the most kills? Get a bonus for that class. Both Tech and Skill? Get two bonuses. Then you max out if you have defenders of all types and they all get kills. That way you are rewarded for bringing other types, but it's based on class so they don't all have to be the same, and if an alliance brings nothing except Mystic class then they don't receive as high bonus and are less likely to win (but still could if they do a lot better).
It's important to keep Defender kills because an entire section of the Champions in this game are best as defenders. If you take that way from them what do they have left? You think Luke Cage & Groot are bad now? Imagine when it doesn't matter how well they can defend. At this point the champion better deal a lot of damage or have a ton of regen or it basically has no use.