I feel like this isn't really that good of a way to get better at a class. For one as a melee dps you have some kind of positional to keep up with and you can't if you're tanking everything. As a ranged dps maybe but ranged dps but I feel like you would get more adequate practice dpsing actual duties and having someone parse for you, dummy parses are one thing but actually pulling out good dps while doing mechanics is something you won't learn much about in a dungeon so far below your level that you don't need a tank or healer for