High level player, low level dungeon: gear, tips and etiquette?

I'm going to give the lower level dungeons a try soon, both for the main story and because I'd like to get my hands on some of the lovely mage gear that drops. However, I want to do them on my CNJ for quicker queue times, and also because my ACN is too low level and I do not enjoy playing pet classes in group situations. But I am wondering:

1) What is the etiquette for needing on gear? My CNJ is 50 so obviously does not actually "need" any gear that will drop. But I want it for looks, and would use it when vanity slots are implemented (and on my ACN, not that it matters). Is this a no-no?

2) How does gear scale when you are down leveled? Do the stats get capped, or is it based on how good the gear is relative to your actual level? I'd prefer to use lower level gear to save on repair costs, but I don't know if that will work.

Any tips would be appreciated. :) Though I'd prefer to run these dungeons on my CNJ, if it would be rude to need on gear then I suppose I can bite the bullet and either wait until my ACN is high enough level or just forget the mage gear and run the early story fights as a damage dealer on my rarely played PGL or ARC.

For 1: Typically I don't Need if there is another mage in the group that is obviously leveling up their class and not level synced. If something drops that I want I will ask if it's ok to Need on it. You can also just ask ahead of time when the run starts.

2: Your gear gets capped to what gear would be at the level you are at. So Level 24 cap sets your gear at item level 24. And yes it is much, much better to use lower level gear in these dungeons because of repair costs and the fact that you get no benefit by using the high level gear anyways.

I've read that wearing level appropriate gear ends up being better than using level sync'd gear. It's probably very marginal, but it's still supposedly better.

As far as looting etiquette, if I have all classes at 50 and I receive a notice that people are new to the dungeon, I'm probably just going to greed on the stuff if I want it. That probably won't stop people from instinctively needing on things whether they actually want to use it or not, but I want to give them the benefit of the doubt.

I've actually been playing a new character, so I will need on everything that's an upgrade for what I'm currently playing and greed on anything that I can use for another class if it's better than something I have. I see no reason to pass on stuff unless I can't have more than one of them.

Thank you both for your helpful replies! :) Good to hear that about gear, I wasn't looking forward to the repair costs. And sounds like I should just queue up as my level-appropriate DPS instead of a healer if I want to get that pretty gear without potentially being a jerk.

Fleur, I like that you aren't a jerk! Thank you from us lowbies still leveling up through. :)