The XP that a mob gives to your pet depends on the colour of it's lvl. So a green lvl won't give as much XP as a yellow lvl. This is why I thought that maybe if a mob would give you more XP (like green, yellow and red) because of the +5% XP, it will also pass over on your pet.
And the reason of this post is because the mobs on this location are much more easier to kill than the ones of other places I've been. And now I realy see the blocks filling

With lower lvl mobs I was shooting ages without anything. For example: Half the way from lvl 61 to 62 I killed lvl 67 mobs. It took me 30 minutes to get till half. On my new place I grinded for 15 minutes and lvled up my pet.
Btw, grey mobs won't give any xp to you nor your pet.