Game mechanic question on experience in a party
 

If I were a level 51, and group with a level 34, who is in range to gain experience with me as a group member, but I kill monsters that are around level 30, which dont gove experience to a 51, does my group member get all the experience, no experience, or partial?

No experience.

Ah okay so in a full party the moment a single person is too high to xp from a mob, nobody gets any. Got it.

Yep.

A level 51 would get such a big piece of the xp “pie” killing blue mobs that a 34 would likely be better off in level appropriate content with a 34 partner.

To expand on this, exp is distributed to group members based on their level, sort of, with the largest share of the exp from each kill going to the highest level person, sort of. Not level, exactly, but the total amount of experience they've gained (the difference is more pronounced once you get to 50+ levels). For a duo of two equal level characters that have varying exp modifiers/penalties, like an assling cleric and a troll warrior, the latter with its 20% exp penalty will always gain more exp from each kill because they've had to get that much more experience to reach the same level as the assling cleric. I don't know the exact calculations, and this doesn't mean exp bars will progress at the same pace just because the person(s) with the penalty are getting more of the exp.

As the level gap between players widens, so too does the exp that's awarded to each player in the group. Of course, some exp with a higher level is almost always better than no exp because you're lfg all day, right? Unless they're so high that you can't get exp, period. There are hard limits to grouping levels and possibility to get exp.

I was grouped at 45 with a 36 and they gained 2 full levels before I gained 60% to level to 46. Yes I got more of the exp, but because I needed more. The flat % gain is exactly the same though.