Before I go any further, I would like to say that I do agree that spins on platinum should always win. I know that I've felt this frustration before, and that it really doesn't help the game.
...
Hmmm... I don't really think that anything should stop people like me, with half upgraded decks, from playing platinum when we can win these special spins. If you can get the epic reward from beating the hardest difficulty in the game... Why not?
Anyone, you or me are NOT entitled to something good just because one of us managed to do something hard. Why? Because people of higher skill or wealth than you or me could farm the hell out of that.
Let me show you with an example which is stripped down of all nuances and specifics.
Imagine a MMO and a boss at lvl 60 with awesome fixed drop and you a lvl 10+ have figured out how to kill it with a little luck but it takes its time.
(compare to elements as someone of a slow and possibly unsteady deck that may, or may not be partially upped, can kill platinum/gold with a little luck 3+ times in a row)
Then some player at lvl 70+ starts farming and killing this monster at 10 or 20 times in the same time it takes for this newbie to do it
(A player with 15+ upped decks that slaughters arena over and over with little danger to itself)
Do you see the problem?
To explain it further :
The sheer amount of advantage the higher leveled/older player gains over the general mass of people will be in no proportion at all to time spent by the lower levled/newer players. There would be even huger gaps in wealth/cards. Thats why a good game got limits and chances. To ensure that people stay in their difficulty range and get rewarded properly for their range, or else the inflation would rise and the longevity of the game would come crashing down. It would be close to impossible to get new players. Everything would become essentially free.
This happens to several games. Where it takes a couple of weeks at most for someone with the know how to get from the absolute bottom to the top 5-10%. Its a dead end for a game.