Hello Dayu! The above posts are correct, INT is usually the main STAT for cres. Those will increase most of your debuff and DoT (damage over time) skills. There are a few skills that use physical attack, and you can use STR to increase their damage if you wish. Take a look at your skill tree and you can play around with what you enjoy! Although, I wouldn't waste points in VIT. The hp increase isn't worth the handicap in damage output IMO. Stay near your tank while grinding and you should not have many problems with low HP.
Generally the skills for this class working well/as intended. A few have some localization issues and some tweaking needed but nothing too major that would hinder your play experience. We're in better shape than some other classes in this department XD
Profession is entirely your choice. I personally chose Artisan so i could make my own gear later on.
I would also suggest you get a mermaid pet as soon as you can, and max the cooldown on pet summoning.
Feel free to ask any more questions if needed!