Variations of this topic have been discussed to death, and it never really goes anywhere. I get it; there's no talking some people into seeing things your way when they like it just fine on their side of the fence. That's okay. But, I have a simple request for you, random strangers on the internet:
If you're gonna queue as a tank, despite not really being one: Just slot a taunt, please. It's one skill slot. You can spare one. Do your group the bare minimum courtesy of keeping just the bosses in one place so we can all get on with our lives that much quicker. We all know more dps can be poured onto a boss if they're not moving all over the place, right? So do the group a solid, and keep em still. You signed up for that (and much more, but we'll settle for just holding still).
If you're gonna queue as a healer, despite not really being one: Same as above; just slot one of the many skills that give health to an ally. Vigor, Funnel Health, Lotus, Breath of Life -- whatever ya like. You have lots of options, and most are pretty good even as a damage dealer. Pick one (minimum) and at least pretend to try and prevent your group mates from dying when possible. If they die to mechanics or bad positioning, that's on them; but send a little health their way from time to time, would ya? Not asking for Orbs, or Ele Drain, or anything else... just a bit of health now and again. Please?
And if you're queueing up to do damage: Well, I'm not sure you can be a "fake" damage dealer... But you can certainly be terrible at it. Try not to be, please? Getting good damage in ESO is about stacking multiple effects and abilities on your target. Try to use multiple different abilities that do damage over time, at the same time. You can overlap them, you know. We see you back there, spamming light attacks as if those little squares at the bottom of your screen are just for show. Put some skills on that skill bar, and use em! Also, realize that the more you move around, unless it's necessary, the more difficult it is for the tank to position things properly and the healer to give you buffs that you want (to boost your damage and survival).
What most of us want when we use the group finder to get through a dungeon is to... well, find a group to get through the dungeon. Oddly enough, that works best when people cooperate and pull their weight. If you signed up to do a job, please at least do the barest minimum of said job. You're capable. You know you are, and so does everyone else. If you just choose not to do it, that's uncool. Please be cool. That's all most of us want.