Just because a spell exists doesn't mean that there are a whole bunch of druids that has 'bring back your arm-shops' in every corner and even if there is a druid that can cast the spell in a village, why would that druid spend WP and risk his life. It is dangerous to cast spells.
Also a little bit strange that you can with a spell bring someone back to life, but you can't bring back a body part. But that's just me.
Definitely. I get your point and I don't think there's anything wrong with ruling like that. There's a bit of leeway in interpreting these rules so I don't see any problem with my ruling, either.
In regards to resurrection, IIRC you don't need the body of the person being brought back, so in my mind the spell creates a new body in the old body's image. When I think of it, I imagine that there is a "blueprint" that a person's body is molded after. It is then exposed to the harsh world and stuff like scars and missing limbs come after its construction. When you bring someone back, you mold a new body after the original blueprint. Elves have been giving the power to alter and remold their own blueprints, which gives them the ability to regrow limbs. This is also why elves cannot be brought back by the resurrection spell in my ruling, and instead their rubies must be brought to the Stillmist where other rituals work, outside the rules and regulations of the other kins.
Note that this is all my interpretation of how it works, a mental model, if you want. In my mind it makes sense. There are a lot of blanks in the Forbidden lands books, and at the end of the day it's up to everyone to fill in the blanks the way they want. It's like when you have people who don't know how televisions work, but everyone still has some sort of model in their mind for them to rationalize and explain it the best way they understand. It could be a simple model or a very complex one. It's not necessarily the way it actually works, though. But I digress.