Constructed absolutly should be the focus of balance, take Leauge of Legends for example (the most successful game in the world) it puts 90% of its effort into balancing its primary mode, they only recently started doing any balance for seperate modes, and they did it by making completly seperate rules and balancing for the alternate modes.
CG has a lot on their plate, and it is way to hard to balance a vastly different casual game mode at the same time as your compeitive constructed ladder. They would need to devote time to banning/designing seperate custom gauntlet card balancing, and they are already stretched thin on resources and time trying to push out a new expansion, mobile, and balancing constructed.
I do think mobile, and balance of both constructed/gauntlet should take prioity over the new expansion, but they are perfectly in their right to decide where they want to devote their resources.
Yes drafting takes a lot of skill, both knowing how to build a deck on curve, making tough choices, knowing the internal meta, and then working with what you get both in the deck building phase and playing. But ultimately gauntlet by its very nature is an unbalanced RNG fest where luck plays a massive part, and thus it will always be a casual mode. And thus is only worth trying to put effort into balancing if and when Constructed is in great shape, and they have spare time to do so.
Now I do think gauntlet should be free but harder to get rewards out of, it’s very strange charging people to play a casual alternate game mode. Especialy since it’s also an area where newer players can go to sort of have a level playing field Spirit-wise in decks. But it is a buisness model, and just like drafting with cards you are gaurenteed a reward for your investment so I understand why they did it that way.
To address the OP, yep Beholder, Reva, and ranged in general are super op for gauntlet, although you should have made that more clear in the thread to start with. Gauntlet is not, and should not be the reason why a card should get changed. If you want gauntlet balancing, this thread should be about that, and not saying a specific card is op, because in constructed where it matters, it is not.
Now if you really love gauntlet/draft you could try to encourage CG to devote some time to balancing it seperatly and if you are just trying to supply some suggestions, more power to you. But remeber they are a small company with a lot on their plate, so try to be patient and constructive rather then frustrated or demanding.