Examples:

Shark (298 -> 257 XP)
Crabman (518 -> 257 XP)
Elekkadom (771 -> 785 XP)
Crustacean (824 -> 842 XP)
Turtle Dragon (681 -> 577 XP)

Obviously, these findings are on the Korean Live servers, so they may not apply to the US servers, but my personal research on the matter indicates that all those experience values are valid for the US servers as well. So, for the 5 monsters above, that is true.

Lineage Playforum also reported that a majority of the monsters located in Fire Valley have an *increase* in XP gained. So, the change isn't all less or all more, it's some mix of the two.

This should be treated as a seperate issue as the level differences some people are reporting.

Ruben tamed a few monsters and noted new levels:
King Bugbear (27 -> 30)
Undead Elmore General (23 -> 25)
Scorpion (24 -> 26)
Troglodyte (14 -> 15)

Melantus noted that this should be welcome news to players since higher level monsters = more experience in this thread: Incorrect Info on Monsters

However, despite the higher level of troglodyte (as an example), the experience is still lower. Before, at level 14, Troglodyte gave 269 XP. Now, at level 15, Troglodyte is giving 226 XP.

So, there are two issues here:

1. Monster levels have changed.
2. The experience formula has changed.

This shouldn't be considered an XP nerf. Some monsters give more experience and from what I've seen, the monsters aren't any harder than they were before. However, what exactly has changed? I sent an email to Melantus showing him the PF findings as well as things I've seen on our live servers - he is looking into it. (Thanks Mel) Hopefully we will have an answer soon.