A Hearthstone match between Rexxar and Thrall would be a bit more intense on an open field with living, breathing creatures. Also the game mechanics would ruin everything.
The clip was made by Wronchi, who is a well-known animator in the Dota community, but his rapid-fire jokes work with Hearthstone as well.
It's the small things: The Random Animal Generator having almost only Huffers, Thrall poking the ground before firing the catapult (referencing that we can mess around on the gameboard), doing melee attacks with the Eaglehorn bow, and so on. All sound about right. Happens all the time in Hearthstone.