Add a new section to each unique summoning portal called collectors corner.
Here’s how it would work:
If you summon a hero it would show up in your collection for that summon gate. For example if you summon Sif she would now appear in your collection.
If a hero was in your collection you would not be able to get that hero again and their chance to be summoned would be evenly distributed amongst the rest of the 5* heroes in that portal.
This would also be true if you got a horghall from Valhalla he would go into your Valhalla collection and then his chance to be summoned would be evenly split between the rest of the heroes you were trying to collect.
If there’s a hero that you want multiple copies of, all you have to do is reset and everything goes back to square one.
Implementing this would allow SGG to keep summoning odds at 2.5% while appealing to the collector population of the game and also provide a unique way to let player go on the hunt for a particular hero with confidence that if they keep pulling they would eventually get them.
The same thing could be applied to 3/4* heroes as well.
If you ever collected all the heroes of a particular rarity the portal would reset and collectors corner would start over with the gates original summoning odds.
I feel like this is a pretty fair compromise between players and developers. I know it’s not perfect, but it’s better than what we have now.