Uh... you get a pretty noticeable message when someone is new to a duty and you will get a bonus so there is little doubt they knew SOMEONE was new.

Also what the heck...

3/The rule of thumb on any Dungeon in MMO is what level is the dungeon or what ilv the loot drop in the dun is the gear lv you want to have when running the Dun. So if you are running a Dun for character lv 30, you should wear ilv 45, any gear of ilv lower than ilv 45 considered under-geared. So take note of that and prepare yourself next time beforehand.
This is completely false... before 50 your gear will almost always be lower than your character's level and dungeon drops are only slightly above in item level. Gear drops are there to improve your character when you do the dungeon at the intended level.

Before 50 your gear should all be within 5 levels of your character level with the exception of accessories which aren't upgraded as often and in that cause you just upgrade whenever there are any new ones available.