this is a nice post with some good questions. for question 2, there were a few guys who were wondering what was possible when the Battle Arena came out. so they put their heads together and did a lot of testing and ended up making these Immortal Builds. there are a few posts somewhere where this is explained by some of the guys who made some of the first Immortal builds. here is a good one.
Edit: just read the post again, and there is a lot of good feed back from players who replied to the original post, if you are interested in reading them.