Still allow type 5's to be camped, since that seems like a popular approach however add them to all named in a zone vs on 1 mob in a zone. Add in a achievement that requires: Hero of Silly Mission #1 0/25 Hero of Silly Mission #2 0/25 Hero of Silly Mission #3 0/25 Hero of Silly Mission #4 0/25 Challenger of Silly Expansion 0/1 Reward: 20 Type 5's of your choosing (all of 1 type)
So you cannot camp a certain mob to get the type 5 you want? And you are giving more to those who can do (box) all 4 missions than they are already getting? Why not just ask for more mission coin per success or cheaper type 5 augs on vendor? Seems like the easier answer.
