I would just like to remind people that the PTR is a testing environment, and thus a whole lot of testing is going on there. The things tested on the PTR should never be considered as set in stone, so please be careful not to jump to conclusions when reading PTR patch notes - things change quite often on the PTR due to the iterative nature of the development process.
If you see something in the PTR patch notes that you do not like, then the best thing you can do is to log into the PTR and test the content in question, and then afterwards come to the forums with your feedback on why you like or dislike something.
In regards to the monster density changes you have seen on the PTR so far; these have undergone a lot of iteration, with a lot of experimentation thrown in as well. The developers were not entirely sure if players preferred more clumpy density with larger monster groups, or a more scattered density with an overall increased stream of monsters, so the developers tried different things on the PTR to see what would happen. It is fairly clear from the feedback we got so far that the monster density and spawn pacing we tested in the earlier PTR stages are preferred, so that is most likely the goal we aim for in patch 1.0.8