What are some of the best places to farm Trolls in Moria. There must be more than the occasional Elite, I'd expect. I was thinking somewhere in The Foundations of Stone, but I don't know where to look in there.
There are a few in Nud -Melek on the west side on sides from the stairs. Foundations of Stone. The Skirmish - Battle of 21st Hall has Trolls. There always one in the Way of the Smiths Skirmish - if you get the Troll encounter you will have two.
Unless stated otherwise, all content in this post is My Personal Opinion.
There are multiple options for finding them, which for me makes it more fun than just grinding the same one instance over and over. You can get them in GS, DN, and Forges, or Foundations of Stone while questing or exploring down there.
I got about half of mine in GS, and the other half running around Foundations (there are plenty down there, just go get yourself lost and you'll run into them). Of course, after solo-grinding in Foundations and finishing the deed, I realized I hadn't done the deeds for trolls in Forges or DN...*facepalm*
The trolls in DN won't count for the Moria troll deed unless you go in in a 6-man fellowship, which is still kind of tough even with a group of 75s only. As soon as you are in a raid (even a 6-man raid), kills won't count towards deeds except for the few kill deeds specifically tied to a raid instance.