In the FoV escort mission, they ARE sending something to clear the way - YOU. Your goal is to be the thing which will clear the way for the escortee. If you do that properly (
see link for details), it will take very little damage until the end when the tower density is too high for the dragon to kill.
Agreed, it was easy until the last part where the zep took too much damage at once. The cooldown on your nuke spell seemed too long and if it was a little shorter it would be better. Personally I disliked the escort mission (I hate them with a passion) but I wouldn't say it ruined the game. I had to do the escort mission 6 times failing right at the last moment in most cases before I got to the final battle. I was at level 46 when I had finished the game and found the final battle when in human form much easier.
My only complaint was the expansion was too much ground based and not enough dragon but Larian have already explained why that is so I'm happy. They listen to feedback so the next game should be even better.
So, no protecting of NPC's or items and if they die / break you loose & no time limits in future games please? The Bellegar challenges on time limits were a pain too particuarly if you got them early into the game and didn't have adequate exp or stats.