XP penalty really that nasty?

[Caridry]

so me and a friend are starting together, and i finally figured out what i would be doing which was making a SK (for SK/shaman group duo) and leveling with him while he was on, and leveling a necro in my own time or when we are on seperately... but it looks like i will be playing the SK full time since i will be getting half the xp as him? Thats a little harsh... or does it even it and i wont really be able to notice it?