What's up with all the NINs Im running into these days?

[Atreides]

This has nothing to do with the DPS being a Ninja, it just so happened that those DPS were Ninjas.
But yeah it usually does more harm than help if a DPS just charges in a group and leaves the tank to pick that mess up, most of the time it ends with the healer having aggro, the DPS being dead which is not helping and the tank having a stressful job because he has to pick the scattered mobs up.
I can see how this is annoying but on the other hand most people by now know what to do and even then as long as 2 people know their shit the fights are pretty self explaining.
So to some people it's a waste of time, as tank you have instand queues but as DPS this is not the case and most people just want to get done with whatever their business in that dungeon is.
I usually just go with 2-3 people from my FC so I don't have to deal with slow runs, if I soloqueue I chill and let the tank do his thing, more often than not I explain in the start of a fight how a fight works as most tanks can't handle my opener without losing aggro because some Warriors think it's a good idea to apply the slashing resistence debuff right away... It's better to let the Ninjas handle that in dungeons.

This. Just tell the healer to not heal them if they pulled something. They'll either learn real fast or rage quit out.

IMO telling a healer to not heal someone is even more of just being a dick.