The only character where I feel like you can actually justify breaking a juggle is Spinal, because he's not trying to juggle for damage, he's trying to juggle to take your meter. If you break a juggle, you don't have to get your meters sucked from curses, and if you can get the Spinal player to start committing to a counter break, you can probably save yourself 2 or 3 extra curses. Purely situational though.