Several fights actually give my characters 0xp since the last patch. With my new character (lvl3), in the temple under glided vale, killing 5 shadows offered me... nothing. No XP, nothing appearing in the log at the end of the fight, it's just as if the fight never happened - except my characters are wounded. I actually had to kill nearly 15 monsters just to get the 75xp I was needing to access the next level.

You only get XP for the first seven kills of each mob I think... then the bestiary entry is at 100% so if you already had killed 7 shadows before the patch then it is no bug

Maybe you had these enemies already in your bestiary?

 

Note: You don't get any XP just from fighting/killing enemies.

As the others stated, you do not necessarily get experience per kill, but rather you gain experience as you fill out the bestiary entry for that particular creature. If you have killed enough in the world to get 100% of that creature's info, then killing extra will only give you their loot as a reward. 

It is a different amount to fill the bestiary for each monster, and this amount is roughly determined by their frequency in the world.

Ok, I didn't notice this before the patch. I'm not a big fan of the "some monsters give you no XP because you killed a lot of them" thing, but if that's the way it's supposed to be, then everything is fine