I feel like Grommash could use a tweak. I'm not suggesting the card needs to be made more powerful, just that I feel as the Warrior class legendary card, it doesn't fit very well into the current meta. I've yet to see a competitive deck that is improved upon if you include Grommash. He is just too situational and in my opinion detracts from overall deck synergy regardless of deck construction, he's more of a "for fun" card.
Frankly, several of the other hero class legendary cards I think could use a tweak as well but I won't bring that into this forum / discussion.
I'd love to hear other's feedback regarding Grommash.