Not even close to broken. Dies to all sorts of cheap removal, responses with hullbreaker's ability are either: bounce the removal, in which case they can just recast the same card over and over again until it lands; or bounce hullbreaker to fizzle the removal, in which case you have to recast hullbreaker for way more mana than they spent on the removal, and have no defense until you do so. I routinely die to aggro and midrange, a wide board with no obvious weak points doesn't care so much what you bounce when they've still got lethal combat damage coming at you.
Amnesigenic#59256
Not even close to broken. Dies to all sorts of cheap removal, responses with hullbreaker's ability are either: bounce the removal, in which case they can just recast the same card over and over again until it lands; or bounce hullbreaker to fizzle the removal, in which case you have to recast hullbreaker for way more mana than they spent on the removal, and have no defense until you do so. I routinely die to aggro and midrange, a wide board with no obvious weak points doesn't care so much what you bounce when they've still got lethal combat damage coming at you.
Tldr: get good