For asking hunter help, you may loose half exp/skill, but in the case hunter creature increases less (increase 10% or 15%? not quite sure) than your solo (increase by 30% if you win). Here is how I do it:
If I have time and do-able, solo
If have time but very hard, ask help from clanmates
If don't have time and kind of hard, pass
If don't have time but very easy, do it quickly or save it for later
I don't think PvP will weak your char significantly, unless you don't do labor, hunter, and merc.
Pvp will be kind of time consuming at high lvl, but much of fun, and you can learn from other players.
But on the other hand, you should do as many labor ect as you can, as you can earn a lot from them to support your better arts in PvP.