People do try to force speedruns still, but they're a lot more lenient during leveling dungeons (Such as level 51-60). Main reason is that the level cap dungeons (50 and 60) allow you to overgear the item level significantly, making it fairly easy to speedrun. And if you CAN speedrun it, why wouldn't you? For the leveling dungeons though, you can be at most 1 level above the entry requirement. And while they can certainly be done with gear one level below the dungeon, that's still not a big ilvl increase... and a lot of people don't upgrade their gear as they level. So, people tend to understand during the leveling dungeons that it's likely either the tank won't survive, the healer won't be able to heal fast enough, or the DPS won't be able to kill the monsters before the tank and healer run dry.

As far as people getting crabby, in my experience people tend to be lenient if you mention beforehand that you're new.