Yes, losing a Familiar is a big drawback. But Heartbeast being moderately useful??? Sure, it's not the most useful for all things, but if it were, everyone should just play Bjornaer and we should erase the rest of the Houses.
Really? If you look carefully, I think you'll see this is wrong. Due to these the Bjornaer can be the best at Certamen, the best at Fatigue-based things (Life-Linked Spontaneous Magic, Life Boost (available via Initiation), Imbued with the Spirit of (Form)), the best at resisting attacks, etc.
For example, years ago someone here challenged everyone to build a magus who could best their Tremere Certamen specialist within the same number of years post-gauntlet. So this was a Tremere expressly built as theoretically the best possible at Certamen. My Bjornaer was so much better it was scary.