All I can say is that a lot of farm groups are not farm groups. Just because you've cleared Ravana EX once does not mean you are ready to farm it. Unfortunately, this has always been an issue in any PF content.

Having something on farm means that you are very familiar with the content. In other words, while different strategies exist, you should be fully comfortable with any popular strategy. So solo or duo tank, swift liberation quadrants regardless of how it's done, traditional or cheese double preys, etc. If you can't guarantee a run with no mistakes, don't join a farm group.

Back when I still did Ravana EX, I joined a lot of farm groups. Even now, when I join clear parties just to help, it's very straight forward. This is what the chat looks like.

1,2,3,4 = A,B,C,D
Tanks A, Healers B, DPS 1/2 C, DPS 3/4 D
Tank 1 goes A, Tank 2 goes C

That's it. If you can't guarantee a 100% clear with those three lines, you are not ready to farm.