Animal Companion gives you a second pet, and causes both of your pets to deal 65% of normal damage. Combined, it if definitely a DPS increase, and currently tuned to be stronger than the other talents on the row in terms of raw DPS output.
That said, the hidden debuff also applies to other pet-based sources of damage (Dire Beast, A Murder of Crows, Stampede, Spitting Cobra, and presumably any trinkets that spawn additional “pets” that fight for you), so take this into account when choosing other talents.