Beastmaster is rather dissapointing, not a fan of once per battle abilities regardless, but this doesn't even provide something new. I mean the two options are basicly a carnosaur's blood frenzy and a stegadon's command ability. The effect themselves aren't terrible, but couldn't they come up with something new?
Celestial destruction is decent enough, mostly cuz of how it interacts with the rule of one and effectivly gives us 2 stomps. That's something I guess.
Still a tad underwhelming for mount traits, especially if that's all we get.
As for primeval domain. It's better I guess. And I assume the more competitive minded players are probably reasonably happy with this. But I can't say it's exactly an exciting rule.
I do hope there's more in there.