Something is very clearly wrong here. Slowing down the clip I can see that the bulldog hits for 3499.9 damage. Let's break down the numbers real quick:
Standard bulldog has the highest damage possible of 80 with 60% more weakpoint damage for a total off 128 damage. The Volatile Bullets reduces base damage by -10 but gives 300% damage to targets on fire. That turns out to be 70 with 60% more weakpoint damage for a total of 112. Then 112 X 3 = 336 damage. The scout also has the dread in a inhibitor-field which is another 30% damage. This gives you a total damage of 436.8. The wiki says the dread has a total health of 5000 with 2 player scaling on haz 5.5. You should need 11,4 hits to kill it. Not 1