Awwwwkwaaaard...
I haven't had much guild drama in my WoW life. Have had a friend of mine who kept being sat because he CBAd to learn fights. One of the 2 GMs in the guild was pretty terribad but was never sat, and when a BoE polearm dropped, one of the guildies teased my friend with it saying he could buy it for 20k (this was during firelands).
My second guild drama was during 5.3. I was in this really small casual guild which consisted of ex-raiders from another realm. At some point, 2-3 out of the 4 ex-raiders (the 4th being the GM) left the guild to join one that was progressing. Now mind you, these ex-raiders have been friends for like 2-3 years and they simply left the guild.
My GM is still sitting in his lonely guild as I went to the alliance side as there was no PVP going on on the Horde side (I was in the guild because it was fairly socially active, which I enjoyed). Sometimes I log on my horde char to do some random stuff and I see him and it's so sad