I don't think the Easterlings would have had mumakil; even if the beasts could stand the cold that far to the north, they were Haradrim animals, from far southern jungles. The people of Rhun wouldn't have had access to them, or the knowledge to use them.

They almost certainly brought siege engines, because Sauron loves those (he had catapults early enough to kill Anarion with a rock during the Last Alliance, and sent both catapults and a ram against Minas Tirith). Catapults are pretty useless against a mountain, but would probably have wrecked Dale. It's hard to see why they wouldn't bring a ram - again, Dale was a walled town, with presumable gates - but without the Witch-King to add sorcerous power, it would just be a normal bit of wood (albeit huge).

We know Erebor had no gate at the end of the Battle of Five Armies, so Dain's people must have made a new one. Given that they'd just driven out a dragon... yeah, I think they'd have made something designed to keep out the next one. Maybe iron/steel, but... mithril? The stuff isn't exactly common, and I wonder whether Gimli's Gate of Minas Tirith wasn't basically a steel gate with mithril trim. I would guess that, if they used any, they melted down some old armour to make reinforcing bars, and built a steel gate around it.

But even that would probably keep out even the most determined door-hitting-stick. ^_^

hS