I've tried Diadem a few times now, and I'm pretty disappointed with it to be honest. I had a lengthy discussion about this with my FC before the patch, and the sentiment holds true to this point. People can and will find a way to exploit the content for efficiency, and by doing so remove any originality or fun from the content in the process. They adamantly disagreed to start with, saying how the zone size and variety of content inside should keep people to themselves and hopefully prevent exploitation.
Day 1 was great, everyone was bright eyed and bushy tailed, and the content was fun to do. Day 2, people have already figured a way to make it essentially one massive fustercluck, turning it into more of the same mind numbing grind. Worse still, get match made with weak players, and you may not even get credit for the actual kills, so you are sat in a group, spamming the same mobs over and over, occasionally getting nothing for it.
I am now abstaining from the content, it isn't necessary for progression, and it also isn't fun.