Paladin tank here.I absolutely loved leveling from 1 to 50,usually most of the people I've played with are generally good or at least not abrasive. Through my levelling and general dungeon running i've found that about:

1).30% of people are really helpful and informative as well as accepting and not just tolerant that others are new. Some people even see the "additional tomestones message" and reply with something along the lines of "yay tomestones or yay new person".
2).55% are more than likely there for a quest fulfillment or a certain drop. I'm not sure how much you've read up, but most of the level 50 ones are requirements at some point, including the lower level ones, to complete upgrades to the current relic weapon (you could also think of it like a legendary/unique weapon). These people aren't generally abrasive and/or may be a bit frustrated since later on dungeons have a 9% chance to drop specific items required to upgrade your relic, and running certain ones can be really taxing, mentally.
3).The remaining 15% are people who tend to yell/kick/are generally rude towards newer players and may also be a bit more egotistical than your average player. These are the people you are probably referring to. Some of these players have things pointed out to help them and the group by, not just by the tank/healer, but the other players in the group as well, but don't try to even read, just assume they are better and carry-on.

If you are wondering which dungeons are "better" for avoiding the abrasive or rude players, it's a crapshoot really. I've run Wanderer's Palace HM several times - most of the time, people are nice, but some are just there for the best time/quickest run for their item/quest completion.

A couple of things, as a Paladin to remember:
1.You are the tank, and generally set the pace of the dungeon. If You can't handle the pace, you can either stop and say so, or let the DPS/healers tank their own mobs. You are trying to get used to "end-game" content as well as everything else so go at your speed, but respectfully don't try and hold everyone else up, if that makes sense.

2.Say that you are newer and aren't as geared up yet - you will probably lose hate to more veteran players with higher gear or Scholars that are switching between DPS/healing; a decent player will recognize this and try to compensate, maybe even CC a little bit, if possible.

3.Don't worry 500% about how you are doing - as a tank, you will get the most flak about things, but you are new and learning. Take the helpful advice and use the other flak to help you do better.