Out of all the enemies I have encountered, 2 star fulings and 2 star fuling beserkers, are the only ones that can penetrate a block/parry. They will also almost always penetrate a regular block which results in one being stun-locked, so as previously mentioned avoid engaging either of them when they have allies present. I use a fully upgraded Black Metal shield, but have never tried the tower shield. I almost always engage them in melee combat when I find them. I wear Wolf Armour chest, Fenris legs & helm, and use the Silver Knife along with Black Metal Shield, and 2 star fulings/beserkers are the only creatures that have close to a 50% chance of killing me in melee engagements.