People in a clan together should not be able to attack each other when out adventuring together. This makes boss fights extremely difficult as we get more powerful. No options to change it as the server is ran by the company. Any changes coming for this in the future? Maybe allow the clan leader to have control over that setting?
Replied in another post already but this will not be changed as it makes more sense from an RP stand point to be able to hit each other there are server settings to adjust this.
The is actually a function of game design and not a bug
You just have to be a better fighter. Learn how to control agro, flank (because it seems you do more damage from behind) and switch out (because you need to heal yourself). Kind of realistic.