If you're not living in United States, Canada, UK, Germany, France, Italy, Spain, Belgium, or Austria, it's impossible for you to get it. It was fine for Khadgar to be an i OS exclusive, because if you wanted a Mage skin, you could always get Medivh.
Meanwhile Tyrande is the ONLY Priest skin, and most of the people in the world won't be able to get it. Hey, im in Argentina, using and argentinan credit card and it worked. I alredy had one saved since my last purchase was sent to Colorado, but i guess anyone can just change the billing addres.
A lot of you won't care about that, or will scoff that I'm being dramatic, but it's a problem that Blizzard sees this as acceptable country settings and change to United States. Because it's a promotional tool with a partner.
It's absolutely ridiculous that they don't have it. Also, these "free" trials just need to go, in general. It's such a sketchy thing to do, they're not free at all, they just hope you'll forget about it so they can keep billing you anyway.
They want people to try and figure out how to use their service and make themselves money. You see that hero portrait in the distance, you can get that. So while both are cosmetic items, they are in no way "exactly the same nature".
And when two players meet up in the world, they will get to see your hero skin and think, where did you get that. In an environment where, say, every class already has 2 or 3 different alternative skin options each, I doubt you would get any noteworthy backlash about an exclusive skin.
Find other ways for those skins to make money; they're a for profit business after all.
Whether it's 15 dollars or amazon prime, it's the consumer's job to decide whether to buy the product or not.