You get an amount of xp based on how much damage you do to that mob, so if your lowbie tags it and you kill it with your pala the lowbie will get much less xp
So basically your pala would be there to minimise the lowbies down time (as they won't need to eat/drink and are fairly unlikely to die).
I was happy healbotting on my priest like this, just following my warrior around and keeping his health topped up, but you might want to start two characters from scratch so you can get a feel for proper multi-boxing sooner.
For a few levels I pplayed my warrior with a same level warlock and it is quite different to controlling a healing slave in the background.
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