Another thing to consider is the attenuation in that Longbrook achieved 76% and your beer is at 83% right now. So your beer is over 10% more attenuated and will lend a dryness which can magnify the perceived bitterness.
I think there are other factors like your palate, the age of the beer, other things mentioned (polyphenols, resins, etc...) and the sheer amount of IBU's present in that recipe.
I think given some time for the beer to drop clear, chilling and carbonating will render a beer different and better than the one tasted today.
Good Luck!