I was at the show yesterday and I agree that Battlecross were impressive.
I love that they have the pit for the Main Stage and am in it every year. Always a good time and it was fun to be up close to Amon Amarth's stage set up as well as the other visuals like Zombies stage show.
Beautiful weather for a show. It is usually like 95 degrees and high humidity on the concrete for the side stages most years (it seems like it at least) so yesterday was killer weather for a show.
You didn't mention Machine Head but they finally came to their senses and opened with Imperium about midway through this tour and it is such a great opener. No surprises in their set followed by Davidian and Aesthetics of Hate which they also added back midway (great choice) and finished with Locust and Halo. They are a killer live band and the new bassist fits them well.
I encourage you to give Mastodon additional extended listens. They are an acquired taste and their sound was bad last night so the vocals were fairly muffled. They need to be seen in an intimate club and are not made for the "big stage" in that they are all about the music and complexity and not showmanship. This will keep them from ever being as big as they should be popularity wise but there were no better musicians on any stage yesterday than Mastodon. Give them another chance. I admire that they choose to follow their own path and not one of seeking mass appeal.