I own Every Champion, so I can basically never get Blue essense

I own every champion, and with the champion shard and essence type rewards thingys, that means that I basically can never get blue essence, now for some reason blue essense is what is required to make the mastery level 6 and 7 bull crap... So I have mutltiple level 6 masteries but I cant upgrade because I cant get a gragas champion shard.... I cant get champion shards at all so blue essence basically doesn't come to me, and I cant get a gragas permanent because, well I HAVE gragas, this is the same case for Wukong, and for Rumble....

Can someone help? Am i boned from mastery level 6 and 7 now because I own every champion???

If so, Giant flaw in system I feel should be addressed.