I am planning on getting the GUILD achievements for killing the last boss in each Legion raid on mythic. We need 16 guild members for this, and 20 people max.
Main fights to brush up on would be Eonar, Varimathras, Aggramar, Maiden, Avatar and Kil'jaeden. Everything else should fall over.
First attempt might be on 2018-12-01 at 20:30 server time. The Plan is to do EN, ToV, NH then AtBT. There most likely wont be time for ToS this time, but we will do it next time. Any bosses that can be skipped will be for speed sake. I only can skip us in EN currently.