Why DF parties fail so much on hard content
Simple reason being, zero communication. Everyone enters, buff and start.
Problems arise because:
1) Players may be new and dont notify the party
2) Players may have different strat so there is no plan that all are on the same page with.
3) Some may not be new but unsure of certain phases
4) Players entering hard content and selecting a language they are unable to understand or communicate in. AKA If you are trying hard content and do not speak a language do not select that language with any expectations of clearing. It just makes things harder for you and for the rest of the party. There is no point selecting a language just for faster ques if you cannot clear that content due to communication problems.
All of those can be sorted (except the language barrier) with the party taking a couple of minutes to sort out a plan and to give advice to those unsure on some mechanics. Instead of all charging in Gung-ho with no coordination.
It's that co-ordination that allows statics to clear content, something which is highly important. Something which doesn't happen with the majority of DF parties.
One person has to step up and act as a leader within DF parties, and the rest should follow. What job they are on is irrelevant as long as one person steps up to the mark and people listen, then DF parties success rate will vastly improve.