Personally, I found no complaint with the end mission. It was easy. You're suppose to use all the abilities you've been given in this mission. On my second playthrough, the Zeppelin didn't even take any damage because I was way ahead of it, destroying everything in my way. The end boss isn't that hard either. Divinity 2 is an RPG that punishes you if you make a crappy build. Make a good build and the end boss won't be that hard. Divine Divinity was the same, if you had made a poor build, then chances are, you'll find the end boss hard along with enemies in the end area. This is how the Divinity series are, you've got to be strategical when leveling up and apply thought. It's not like Oblivion where RPG elements don't play any role.
@candlebbq
Bellegar doesn't die in any version. The third person walking with The Divine and Zandalor is General Augustas.