Just check how big part of the screen shadowed by the gun.
These problems just show either the developer or the QA never actually played the game.
And this one is asking for over 20 bucks. Does this make any , I mean, any sense?
I put the screenshot here
imgur dot com/a/5m0ugzo
Not sure what the price has to do with it…
But they are usually within set boundaries in terms of size on screen
Maybe it’s something they should adjust, but if it’s within the boundaries, not sure what QA are supposed to do (the QA team don’t test skins anyways)
I do not know what is " the boundary for guns UI".
In Ashe’s case, this is a scope UI which might cover a larger part of screen than the default Ow1 or OW2 skin.
Why people would pay money for a skin which:
1 You can not even see the skin most of the time yourself.
2 Put you into a disadvantage in gameplay.
This issue happened on multiple Ashe skins like Raijin and Tiger Hunter skin.
And now we got another example here.
For me it leads to 2 points:
1 The developer / model designer actually do not spend anytime play the character they design.
2 The QA guy who test the skin behaviour do not do their job to consider the gameplay impact, only testing with tech glitch.
If the game company does not even put resource to output a good game experience, why they would expect people to put any money on it?
If you want player to pay real $$ to your game, at least show it to public that you care your own game!
I get that people might put money towards a skin, but at these prices, they would likely just buy the one or two skins, for their favourite hero.
If it puts you at a disadvantage, then yeah, that would be a reason to not buy/use that skin 
In an ideal world, the artist/designer/modeller/dev/QA/various other stakeholders likely would of all had a say in this and would of had an opportunity to raise queries/observations/bugs around the skin, in terms of how it looks, and how it plays. Who knows how much of this Blizzard does.
I have to agree with this in regards to your last sentence, I really do not think that they invest much in terms of quality assurance.