The Night Blades used the "
Thug" monster stats. As the link mentions, they are considered a challenge rating 0.5 creature.
Five 0.5 CR creatures is considered a deadly fight, but just barely, for five level 2 characters. You also had Red Beard on your side, so it should have evened things out to make it hard but fair. So I would say yes, this is normal. A big disparity in the quality of rolls on each side tilted the scales, but some more involved planning on everyone's behalf would have given the party a better advantage from the outset.