Being kicked from a dungeon is never fun, especially when you don't get any feedback why you got kicked. I noticed such behaviors on my second account where I only have something like 340ish CPs. I still remember receiving some whispers after being kicked that they felt sorry as they obviously kicked the wrong guy. I did like 70%+ of the groups damage, even with low CP as the 1600 CP guy in that group was probably semi-afk or the like.

Kicking based on CP values is just stupid IMO. At least watch them play for a while and if you think s/he's not up to the level s/he needs to be, talk to him/her first and state your problem with his playstyle and how s/he can improve. That IMO is part of a feedback loop and may help the other to improve. I usually play tank and especially on low-damage groups I have a lot of time to watch others play and I at least try to give hints on how they might improve. Unfortunately, not everyone accepts critique and some simply do not care at all or get even defensive like I threatened them somehow.

With that being said, 1200 CP+ is also no guarantee that the player actually knows how to play "properly". No offense to the OP, but I know some players who retired and now have lots of time to play ESO but they don't play on a level a 20 years old kid is able to play the game. And this is partially visible in how they play. Correct waving and light attack animation canceling allows players to increase their damage done by a way to large margin. Rich Lambert, creative director at ZOS on ESO, did mention in one of this recent streams (www.twitch.tv/slashlurk) that they, ZOS, should do a lot better at explaining the mechanics involved and guide players on how to utilize that mechanic. They are also aware that there is a large gap in dps done by casual players or ones that don't utilize those weaving/animation canceling "techniques" and ones that do. The problem is not that players do not play to their fullest potential but that people just want the meta so simplify even the most-trivial parts of the game. Instead of grouping with various players, learn new people on the way you can talk to and have a good time, the soul purpose of those dungeon runs is to get it done as quickly as possible with the least amount of social interaction necessary just to obtain loot/transmutation crystals. And if you don't play at a "decent enough" level you are considered a burden rather than a help and people might start replacing you with someone other. This though is less a problem of the tool ESO offers than it is a community-driven issue per se.

The best advice here is to grab 3 of your friends in the end and run dungeons (or any other content) with those.

My personal horror story is going through through one of the vet (non dlc) dungeons, getting to the last boss with little issue, then getting kicked because the rest of them wanted to invite a friend of theirs in to complete the dungeon.

They literally said something like "A friend of ours just logged on, we are going to kick you so we can get them in. Sorry." And that was it.

I basically stopped doing group finder, and I only do dungeons now if people I know need someone to fill in, which is pretty rare.

In other words, I have stopped doing dungeons for the most part. I have eso+ and basically two of the four content drops per year mean little to me.