I never faced Harpy Wraith maybe i have to begin somewere with a WorldBoss.
I'd say the boss near Sanctuary is the best one to start on.. although he does have a relatively strong metal attack every so often aside from his physical, as a word of advice. Shadow Doll I think it is.
~ you wanan go alone or with others?~ whats your class?
Psy is hard to kill world bosses alone so you will need a Tank and DD's.Since they are so easy you just need a Sin to do this lol or a BM also works, any class that can be 5.0 will be fine, except the archers, cuz their damage are crap when they r on 5.0 mode lol.
i would say spearman, hes pretty easy...if im not wrong, he only uses a mana drain aoe, nothing special.