They shouldn't need videos and telling them to watch them is treating the symptom, not the disease. They should be able to learn the fight mechanics because they aren't that difficult most of the time. When I played WOW my guild did the encounters ourselves through trial and error, observation and communication. We tried to be laid back about it and didn't blow up at people over mistakes because that never solves anything and anyone taking the game that seriously is probably a drama queen anyway. We didn't win server races but we had a good time and it got done without consulting tutorials and videos which is like filling in the other half of a crossword.
The real problem with WOW is that its old and there are no surprises left. It's obviously being kept on life support just for the cash while they work on new games to sustain them going forward. The people behind the inventive and original parts of WOW moved on already. No game lasts forever, they did a pretty good job of keeping us all entertained this long.