Hello there,
I have to completely agree with the OP.
I am a LVL 127 C1 Cleric C3 Priest C1 Chaplain (fresh) and leveled in a party most of the time. In all of that time the other party member got 90% of all loot, no matter which looting system (tried it with a friend).
Hence (since I also need to buy items for my skills) I struggle with money all the time, I never have the ingredients for a recipe except when I go farming solo and I almost never get equipment drops.
Leveling like this is frustrating as hell. Additionally, people don’t seem to be aware of this issue and I never encountered someone who was nice enough to actually share even if he/she didn’t need to.
And concerning nizidr’s comment: There is a whole class section that is predestined for more supportive builds. Yes, you can do damage with each of them. But most of those builds to not allow a damage output nearly as big as those of wizard, swordsman & archer dps classes. Which should be okay considering that we can do awesome support and heals. So sure, it would be very naive to think with your so called “Trinity role mentality”. But since it is possible to go full support (which people never seem to dislike in dungeon runs), it should also be possible to level decently in a party without those major disatvantages.
And for those saying, that I could always level solo to get drops: Yes, that is always an option. However, I have a similar dilemma there when I need to fight for a mob (which is often). While Wizards and archers can nuke anything at range, swordsmen just outrun my while waving cheerfully. Most of the time, when I get to a mob, it’s already withering away. And if I manage to get there early… well. 
For me, this is a game breaker. I was expecting a game with a great atmosphere perfect for a shared leveling experience. Which it is. But apparenlty not for supporters.
Please fix this.