Scarabeus is usually not very difficult to kill. The minion beetles are fairly weak, so they can be easily avoided or killed. You might as well ignore them, they die along with their master anyway. The poison darts can be dangerous, if getting hit by multiple or all of them and the character is lacking poison resistance. Melee fighters should go for a high poison resistance. The attack uses a distintive animation and the projectiles move somewhat slow, so ranged characters can try to simply dodge it, thus can get away with low or even negative resistance. The projectiles have a chance to miss if wearing % chance to dodge projectiles equipment. You can also use the bookshelves in the chamber to take cover, but don't let yourself get trapped in one of the corners.