To the point of the topic, SE has already started implementing class/level-specific gear. The lower-tier world-roaming NMs have a class restriction, the gear dropping from the dungeons has a "required" rank + some class restrictions. So, you are getting what you're asking for.

To the point of ARC being able to wear the same stuff, one of the better pieces for LNC/MRD/GLA(DD) is Solid Scale Mail from Ogre. And ARC can't use it... /shrug.

Sure, ARC may be able to equip a lot of the first-released equipment..... but if you're subbing out things that have bonuses to STR/DEX/Att/Acc for better Prot gear... well... you're doing it wrong. And like has been mentioned, if the gear you area wearing does not list your class as a favoured class, you receive diminshed returns for the stats on said piece of equipment.