Duty finder you are allowed to "wing it". That is what duty finder is for. Its to link up with groups quickly and easily so you can do content. Last I checked, there is no prereq in duty finder that says "must know the fight". Part of the fun in trying something for the first time is learning it on the fly. Besides any group that isnt full of brain-dead flesh bags will summarize the mechanics to all newcomers. This is how we used to accomplish things before youtube.

If you're entering an organized group, its a given you must meet their expectations. But duty finder is duty finder, and I find that no such requirement should exist.