It seems like the Eldar building teleport isn't obeying the range rules for building placement

If it's the webway gate, it's normal. If not, I'll check it.
Be aware that you can 1st buid or teleport the webway, then build or teleport a classical structure close to it

After a second game I think I was mistaken. The range is just further than I expected it to be.

Well the Death watch kill team is using storm bolter sideway like a gangster