They are indeed, javcs!
Yeth hounds: last of the trio of man's best fiends. They're medium-sized and have the outsider type, as well as the Evil and Extraplanar subtypes. 3 RHD are a decent starting point, but what else is there?
Ability scores vary between low (6 intelligence) to high (17 strength). The overall array is more than satisfactory for a 3 RHD creature. Speed is good: 40 ft. over land and 60 ft. of magical flight. Natural armor is far higher than one would expect, providing the same protection as full plate does (albeit being harder to enchant). DR 10/silver is extremely useful at all levels where getting stabbed by pointy bits of metal is a danger.
Yeth hounds have a single bite attack that deals moderate damage and, in keeping with almost all doglike monsters D&D knows, trips the target.
A far more powerful ability is Bay. Although it's sonic, mind-affecting, and fear-dependent, and therefore blocked by lots of stuff, it's also a save-or-suck with a massive range. Do make sure to immunize your allies to it every day!
Considering the good chassis, flight, and useful save-or-suck, as well as the decent advancement potential, I think at least +1 LA is warranted here. Do discuss.