Rng is good for the game in blizz's mind because most people don't have good luck, so they have to go back and farm x boss in y raid even if it's raid finder could be an upgrade. Which although monotonous it adds some longevity to the content, if you're casual and don't do reg raids use the valor upgrade system. It's quite good, if you miss out on a piece you want you can upgrade something else making you feel like all your effort isn't wasted.
If that isn't enough buy valor gear, sure it's frustrating if you're trying to get your 4 set bonus but if you had it right off the bat would that excitement really last that long? I also heard someone say they should implement a quest for raids, they did this for sha and I suppose you could say the legendary drops are an extra quest (although i don't know you'd classify a gem as gear:P).
System is fine, part of what makes it good is the anticipation. The only thing I could say they could maybe change is the amount of gold, but then if they made it too much it'd make people grind. Personally I say it wouldn't be a bad idea 150g per boss no loot 50 gold per bg win, something to take the sting out of losing and resulting in qq threads such as this.