To me, the difference between providing additional XP through farmable items and through just having a higher XP rate is that the farmable items are typically more versatile in their uses. We see this with task completion tokens, for instance, in that you can give them to other characters or turn them in to the gambling NPC to either make bets or convert them into gold. Likewise, kill task items can be given to your other characters or sold for decent profit. Even snow provides RvR task participation credit and generates traffic to docks.
Phoenix eggs are an anomaly, though, in that there is literally no use for them outside of providing extra XP to the character that originally looted them. You can't sell them, not to another player nor to an NPC, you can't give them to the gambling NPC for anything, you can't hand them to any of your other characters. You hit level 50 and literally the best course of action related to leftover eggs is to destroy them to free up some inventory space.
Since eggs don't have any of the versatility of other items that can provide bonus XP, I suggest that they simply be scrapped and the bonus XP that you would've gotten from each looted egg gets added to the normal XP rate for soloing (and only for soloing since this is the only activity that generates eggs in the first place). There are three benefits to doing this:
1) It frees up an inventory space while leveling. This can be pretty important considering how easy it is to amass drops. Particularly for new players who can't salvage items and are unlikely to own a merchant NPC, it would be nice to have at least the one extra slot.
2) It's less confusing to new players. If you're just starting on the server, you might have no idea what to do with all these eggs you're getting and then miss out of the XP you could've gotten until much later when you finally figure it out.
3) It makes XP rates more transparent. It's really hard to figure out when grouping, for instance, is actually going to yield a higher XP rate for you overall than soloing and turning in eggs will since you have to do a bunch of math with a bunch of unknown or only vaguely known values (e.g., how much XP does each egg provide at each level?).
Alternatively, egg could be made tradeable so that they can be passed on to alts or sold to other players. However, I think this is a clumsier option since you can only collect eggs while leveling. Typically, if you're farming items to sell, you're probably level 50. If you're not level 50, you probably won't want to sell eggs because you want the XP for yourself. The better option seems to be to just scrap eggs altogether.
Phoenix eggs are an anomaly, though, in that there is literally no use for them outside of providing extra XP to the character that originally looted them. You can't sell them, not to another player nor to an NPC, you can't give them to the gambling NPC for anything, you can't hand them to any of your other characters. You hit level 50 and literally the best course of action related to leftover eggs is to destroy them to free up some inventory space.
Since eggs don't have any of the versatility of other items that can provide bonus XP, I suggest that they simply be scrapped and the bonus XP that you would've gotten from each looted egg gets added to the normal XP rate for soloing (and only for soloing since this is the only activity that generates eggs in the first place). There are three benefits to doing this:
1) It frees up an inventory space while leveling. This can be pretty important considering how easy it is to amass drops. Particularly for new players who can't salvage items and are unlikely to own a merchant NPC, it would be nice to have at least the one extra slot.
2) It's less confusing to new players. If you're just starting on the server, you might have no idea what to do with all these eggs you're getting and then miss out of the XP you could've gotten until much later when you finally figure it out.
3) It makes XP rates more transparent. It's really hard to figure out when grouping, for instance, is actually going to yield a higher XP rate for you overall than soloing and turning in eggs will since you have to do a bunch of math with a bunch of unknown or only vaguely known values (e.g., how much XP does each egg provide at each level?).
Alternatively, egg could be made tradeable so that they can be passed on to alts or sold to other players. However, I think this is a clumsier option since you can only collect eggs while leveling. Typically, if you're farming items to sell, you're probably level 50. If you're not level 50, you probably won't want to sell eggs because you want the XP for yourself. The better option seems to be to just scrap eggs altogether.