You made great points here DaP, but it isn't hard to train multiple fenris wolves, and they won't die to any human soldiers, but will only die to jarls and hersirs. With decent micro, you can use them effectively in battle without them dying...
Also, I usually as all civs have quite a few temples for a few reasons...
- Greeks need favor and have collosi.
- Norse can build anywhere and MU are some of the most devastating battle-changers you can have.
- Egyptians have those beautiful mummies, scorpion men, petsuchos, rocs, well... egyptians I think just have the best MU...
- Atlanteans have heka-gigantess which are great to bring in to the battle but too slow to run from the other side.
Now, simply because hel makes them train fast does not mean that you can gain the favor any faster, either way you will be running MU faster than you are getting the favor to train them, so why sacrifice 1-2 MU because you wanted them to train faster.. this is why you get multiple temples. IMO favor is too precious for norse to waste.