Kill Tasks isn't on this server. At least if you're talking the level 1-20 tasks you get from named guards.
Xp Items that you turn in have a limit of 11 per item. You can only turn in that stack of 11 once per character. i.e. 11 Ghostly Essence, 11 Trip Wire, etc. per character.
There are a ton of different level ranges and items available to turn in, though.
I tried to make low tasks in midgard and albion, but the reward was just very poor. And drop rate of needed items was very low. They are not worse to do them there. In Hib every mob droped the needed item and it was a good compliment for the solo leveling. But also not high enough at all. I dont know what about rewards on higher levels.