Duuude that happens to me sooo often....
BUT, when I'm upgrading low lvl gems and run into a 60% chance (like twice or 3 times) to upgrade it to lvl 50 or w/e somehow i do seem to get 3/3 4/4 5/5
So the fails only happen when I actually try to get a gem to a higher level then achieved before (I'm seeing patterns!!! but yeh prolly just badluck & RNG)
I also have spent 7.5k shards with kadala to get a Raiment helm and i think that's alright, the idea is to have an extra chance of getting that specific item after finishing an "X" amount of grifts. Instead of having better chance while gambling with shards we should have a drop focused on items we are currently wearing, at least we would have a decent chance to have more ancients with good stats and/or rolls and then you can go to kadala to look for any other item.