Matewis: Hearthstone was a lot of fun as well. But might be expensive to get into nowadays after all the expansions.
Hearthstone suuuuuuuucks. It sucks worse than my high school poetry. It sucks worse than playing D&D with drunk people... ok no, I take it back, nothing sucks worse than that. But still, it blows. If anyone really wants to play an online CCG, I recommend
Magic the Gathering Arena. I mean, Hearthstone is basically just a dumbed down Magic with way crappier artwork and annoying random chance elements. And Arena is... well, simply MtG, which still means about as good as it gets wit CCGs.
And yeah, I also recommend Path of Exile. To be perfectly honest it's been a long time since I played it so I've no idea if it changed a lot, but back then it was a ton of fun, and best of all it didn't feel like an online game at all (though that may well mean that it's not what the OP wants).