I think It's perfectly fine, You wouldn't buy a pack of cards and complain you have a duplicate If you knew there's a possibility of that happening or upgrading a weapon only for it to fail 5 times in a row..... It's random chance the way it should be. You are aware of that It's random and there's a possibility of It obtaining a stat not to your hero's needs so deal with it you wasn't forced to sanctify your hero's sooo......

It would be a poor decision to take away them odds because then there would be no risk factor you know your hero will get a stat he can use 100% ergo pointless having a random chance at all.