This big red dino is a great Ferocity pet with a specialty in sustainable damage over time. Its Monstrous Bite builds up over a period of 30 seconds to an additional 9% damage on all the devilsaur's attacks. If your battle is going to last 30 seconds or less, though, you're not going to get the full benefit of that, especially if, as in PvP, there may be breaks of a few seconds in which the Monstrous Bite buff is not being reapplied, then your devilsaur will have to start over again. This makes me think that the best utility for a devilsaur is in instances, particularly on long boss fights where it can just wail on a target from start to finish. Just be sure that your tank doesn't mind the footsteps -- they're not as loud as the core hound, and they don't shake your friends' screens, but they could definitely get annoying sooner rather than later.
This was the first exotic pet that BRK caught on film, and it comes in shades of red, white and black. You'll find them all in Un'Goro Crater, except for one more in the northernmost Netherstorm biodome as well.
The closest non-exotic pet is the raptor, with a Savage Rend ability that does some bleed damage and boosts attack power if it critically hits. It has a nasty 1 minute cooldown though, which really limits its usefulness.