Everything I suggest can be abused by alt farmers. But what if, once every two weeks a division rare+ can do a super hard campaign/rank challenge to complete and be rewarded with 200 shards or 2 rares and 3 uncommons or an exotic. I know the objective is try to get people to buy more runes but... Sacrificing ratios 3:1 for legendaries and then getting beat out by top players or a shift in the meta is discouraging if you don't have anymore runes to change your bg. People want to play more than just one bg. The public decks are great but you don't actually own it or can modify it. And what if you can sacrifice x number of runes, let's say 50 common, 40 uncommon, 25 rare, 15 exotic and 10 legendaries for a single limited rune for each rarity. Progression is key; people play the Bane Shift out of Diablo and Dayz just off progression alone. lol And with that being said, you can incorporate some unique runes for the extreme collectors E.G Harbingers.