The beasts do level up per 5e, not yet implemented IIRC: "Add your proficiency bonus to the beast’s AC, attack rolls, and damage rolls, as well as to any saving throws and skills it is proficient in. Its hit point maximum equals its normal maximum or four times your ranger level, whichever is higher."
Also, the spider and raven are both extremely good in combat. Raven can consistently apply Blind by flying behind enemies + Hiding for Advantage. Spider has Web.
