XP penalized for helping in challenges

[Mythic]

One, doing challenges that you haven't done before don't give XP they drop gold, diamonds, AP, CP, and Base Damage.
Therefor any reward for doing challenges already done would consist of gold, diamonds, and AP, and what you would get is something like arena you got the first time rewards now they well be 10 times less, and maybe even limited to once a day per duo and group challenge.