Since when did frenzied boar boss packs spawn?

[Baajikiil]

Are those flying things that spawn from these bosses/minions any tougher compared to their normal versions or are only the nests more difficult to destroy?

No. Now that would be interesting.

Those bosses can sure be a handful in hell though; if they spawn with an aura, they can flood the screen with semi dangerous crows in a very short amount of time. And it takes a while to kill em with the increased hp.