Since I'm an avid Hearthstone player I'm intrigued to hear that your developer is into the game as well. I guess you don't really have a GUI to show off yet? Not even a placeholder / concept art? I really love the way Blizzard designed the Hearthstone board and cards. I hope that you can take what they did right and create something that is still uniquely your own.
My opinion is that Hearthstone, unlike other digital TCGs, reached such a large success not just because of the existing Warcraft fanbase, but because Blizzard was able to create a "magical" atmosphere, together with great flow and feel to the game play aspects.
Other TCGs have tried, but I feel that games like Magic the gathering, the recently released Eternal, and the Elder Scrolls TCGs all fail to accomplish what Hearthstone did: they feel stiff and boring. Hearthstone is fun and fluid.
I hope you take my words into consideration when designing the game. As an avid TCG player (and investor in the developing decentralized gaming space) I really want to see your game succeed.
Best of luck. And if you have a slack channel I'd love to join. Otherwise I'll keep checking in here from time to time. And I'll buy some Wood cards.

I like to collect things.