I will say that I do enjoy the hell out of Hearthstone
I was addicted for a few months when it was still in beta.
The paucity of cards resulted in a repetitive experience that ultimately became dull. Additionally, RNG seems to play a more prominent factor in dictating the outcome of a match when compared with similar games. This effectively normalizes the skill gap at a specific threshold, resulting in diminishing returns in terms of the temporal investment.
I've seen plenty of "professional" players go 3-3 (or worse) in the Arena, even with competent decks.