How would you break it to someone that their DPS is awful?

[Seiryuukishi]

I would let them be. No one is going to be great at everything. Sure there is always room for improvement somewhere but don't call them out in front of people. That's disrespectful. Wait until the run is done and pull them aside, If they're on your server or in fc, and explain to them you noticed a lull. If you play that class offer tips and even show them on a training dummy. Visuals help a lot. There are better ways of handling this than being a douche bag lol.

[Tiggy]

I would let them be. No one is going to be great at everything.

We had a FC member who was quite honestly as awful as the OP's scenario. Every party would noticeably be hindered by their presence and it was detectable without any parsers. We let it be too and in the end you know what happened? He was always left behind on the sidelines because people started avoiding him for any and all content. This passive aggressive solution isn't a solution. It's running away and not dealing with it and in my experience it made things worse and made that player feel ostracized. Be direct and kind but don't ignore it.

[Seiryuukishi]

Snip.

The trouble with that is this generation of gamers have this illness known as "entitlement". These players have to deal with crap shoots as to what sort of behavior they'll get in regards to gameplay because as previous comments have shown a lot of people take this game WAY too seriously. Screw up in Coil one time? You're a social outcast. You get kicked, the babies throw a hissie fit because thirty minutes of twenty-four hours didn't end in perfection and people wonder why most don't even bother trying anymore. With a player base like that who in their right state of mind would blame them for not giving a rat's ass. But then when they encounter someone who genuinely wants to help without being asinine or wanting to come off as such they're already on the defensive because? You guessed it. Morons who think they got life all figured out because they beat a raid. Kudos to you guys. You accomplished nothing important.

But no my intention was that you don't call them out in raid otherwise you get previously stated behavior. The "Jock and Nerd" mentality needs to gtfo. Time to grow up and act like you have some manners (not you personally). Ignoring the problem does not make it vanish but neither does getting bent out of shape over it either. If you're only solution to a problem is to lose your temper keep your mouth shut and go live in the woods. You belong with the beasts in the wilds.