I've been playing MtG since I bought my first Unlimited starters from Waldenbooks. I'm not new to playing around cards. I really don't have that much of a problem with Mind Control in constructed play, since you are tailoring your deck and can accept certain risks with deck design. Not the same in Arena.
I would say Mind Control is only broken in arena - where you can have more than two and can't tailor your deck to answer any of your creatures being stolen.
I still think it needs to be silencable (silence mind controlled minion returns it to you) or have a duration attached - because it has a built-in two for one value, which most cards you have to work for in order to get. Coupled with priest's innate ability to draw cards through other means just exaggerates its broken-ness.
You've played MTG enough to know that if you get your shit stolen you CAN have answers to it that don't involve destroying the mind controlled creature. You can destroy the enchantment or source of the control. You can use return each creature to their owners hand spells, etc. In Hearthstone if your creature gets stolen it is never ever yours again, and you've lost tempo and you now have to deal with the card you dropped. Removal for it is fine, you can use a Big Game Hunter if your newly dropped Ragnaros gets stolen, but that means you can't shoot their Big Bad Creature after you drop your BGH because you had to waste it on your own creature.
The only time it isn't a net loss of tempo, control and card advantage is if you use a board sweeper to kill it, and even then you only break even on tempo.
Edit: And yea you can't compare Mind Control to Hex or Polymorph - That's quasi-removal. It's more akin to a wildcard damage spell - no matter how big or bad your creature is, it gets killed. But it's worse than that, because not only is it essentially killed for you, but now your opponent has it on their side of the board.