Unfortunately, I have no time to perform any changes to the mod due to all my time being consumed on another project.
I'm not sure if you're using your spells correctly for Daert.
Frost Grasp and Kamikaze are very effective against the spider stacks and don't forget your Evil Book.
The starting units will bring you to the Shelter without any issues (I played a couple of times on impossible so normal should be cake) as long as you grab all the crystals and get your Evil Book at least to level 1 (if you get it to level 2 even better).
Note that you may have to skip the big Spider stack in the Catacombs - no biggie you can always fight them later.
Evil Book is your key to winning most battles and any troops that you find dying easily against the shelter stacks stick them in your garrison / reserve. Check the no loss posts here for other information to help you with your strategy (I have quite a few in the impossible thread where I was able to do no loss Daert with the original game files if you got a certain spell from the Ore Cart by the Dwarf castle).
Good luck - keep trying!
/C\/C\