The chopping from the inside is a trope I really don't like, but it actually makes sense for whales, who I believe don't chew.

Even if those 2 haven't died yet, they have screwed up too much to beat 3 whales now. Only a deus ex machina twist could allow them to win this fight at this point.

It's funny how they brought squads of mounted knights literally as fodder. The elites deal damage, the mages irritate the whale, while the knights tank the whale's attacks by actually dying.