Hearthstone, yeah, though I feel it's balance issues lie far deeper than specific cards or deck setups. It struggles from a lack of a best-of format, which means luck-of-the-draw can have a tremendous impact on performance as you don't get to switch cards with a side-deck between rounds against the same player.
It also struggles with an overperformance of Legendary cards (acceptable in itself, they're Legendary) in combination with not having a simple limitation on them. I would have thought that given how legendaries perform strong unique effects and how they worked in WoW, decks would be limited to a single such card (possible two copies, but can play only one, to account for bad draws). This would allow even stronger legendaries as "deck makers", but otherwise limit their power as removal cards could get rid of them though you trade the removal for it ofc.

Heroes OTOH I feel is surprisingly well-balanced. Given how unique their heroes are comparing other MOBAs, I would have expected balance to be all over the place. Yet the stark differences when comparing heroes on opposite ends of the spectrum (say, Abathur vs Lost Vikings or Nova vs Stitches) makes balance comparisons difficult, and actually enables a balance more based on team total output rather than individual hero balance.
It's pretty good. There are individual effects which are over- or under-tuned (Murky's egg, Vikings' Longboat Raid, Hammer's BFG vs Napalm, etc). But these usually come down to limiting build diversity, not messing with overall game balance (granted, Murky excepted as his imbalance is the core of his design, making his basic idea underpowered as he is still feeding too much when being killed).

Still, Heroes balance is impressive. More so than DotA2 or LoL IMO because so many heroes have such weird loadouts yet they balance well enough.