Spvp is insanely unbalanced right now, mainly because of bunker D/D Ele... if you want to be competitive you can run 4 of them and a guardian or w/e the hell you want and it's literally an automatic win every time. Since you don't need to level a profession to get into pvp though you can roll whatever you want. Testing a character out in pvp in GW2 takes all of 5 minutes to do the pve tutorial then hitting 'enter the mists' on your menu. You get scaled up to 80 and given armor and weapon merchants.
Out of the professions you posted I'd go either ranger or necro which played right can hold points fairly well in pvp. All proffs are ok in pve, but engineer surely could use a buff as they only have one viable use in pvp, which is blowing people off points with turrets... outside of that they are fairly useless. I don't think I've died to a eng in months.