If they don't know, its because they don't want to. I don't get why people keep kicking the can down the road on who to hold responsible.
When some first plays a game. It is their responsibility to learn it. How did the Very First 50 Warrior know to get Provoke? They tinkered with it, they read how cross class worked in the ingame guide. Then they told their friends who told other friends, and then someone posted a forum post and spread it further until there was a website one could find on google.
Why don't we hold everyone to the same standard as the first pioneers of a game? If it was that archaic, then no one would have Provoke other than Paladins. The difference between player skill is how much effort into learning the game, practicing their mechanics, and adapting to new situations.
If someone doesn't have provoke, its because they didn't put in the effort to know that they need it, the effort to get it, and most likely didn't think they needed it. If they leveled a DRK to 60 and entered content that needed it. They learned right then that they should have made more of an effort with their role. And even then there's a likely chance they won't care. Short of giving it to them automatically, and then locking out abilities except for it, they probably still won't use it.
Its common decency to make sure you don't let a group down before entering a group goal oriented duty. If you go in there without the proper tools. Then you let the group down. This cannot at this time be done by 'accident'. 'I didn't know' actually means, 'I didn't care enough to look it up.'
But its easier to blame the game and tell the dev 'fix it for me'. Then it is to hold a person personally responsible. If you kick the can down the road, you eventually will have to deal with it again. In this case. Sure give it to them. But what will you do when they 'don't remember to use it'?
I'd deal with them now. Even if its an 'innocent' (and I don't believe in 60 levels of innocence in this case) then they will still learn. If they are as altruistic as you all claim every newbie to be, then they will right their wrong. So in the end, everything works out.