Bulette lost some health before it moved. Then it ran and jumped into the midst of three of them. Down went the Mage and Cleric, and the Fighter lost almost 30 HP out of 56. Then it bit the Barbarian, and he lost something like 24 HP. They pummelled it a few more times. It jumped. Down went the Druid, and the Barbarian lost most of the rest of his health. Then it bit the Barbarian, and he went down for good.
Rogue stabbed it with her short swords, then the Fighter finished it with two swings of his longsword.
Bulette fight via Tabletop. Two rounds. Most of the party wiped, and they were on average Level 5.
Bulettes are supposed to have +7 to hit and 4d12+4 damage per bite. Then, when they jump, everyone makes a DC 16 Strength or Dexterity Save. If you succeed, you don't get knocked prone and you take half damage, but you are still pushed 5 feet away from it. If you fail, 3d6+4 piercing + 3d6+4 bludgeoning damage. That's 6d6+8 damage total to everyone it lands near.
So yeah, is the Bulette SUPPOSED to be too tough for 4 level 4 characters? ABSOLUTELY. It was almost too much for 6 level 5 characters.
Should the game be a party of 6 and set to D&D stats? It should at least be an option for those of us who REALLY want a genuine D&D experience with a real challenge because if you gave us a real Bulette fight and let us be Level 5 or 6 by the time we go into the Underdark, with a party of 6, our characters would not be slaughtered by it, and you wouldn't have to nerf the creature to avoid pissing off your entire fan base.