If I've got prophesis and factions could I creat a warrior assassin on the proph camaign or would I need to play through the factions game to have that combination?
Ah, ok, this will take a bit of explaining. Basically, you can only CREATE a character in each campaign comprising of the professions existing in said campaign so, in prophecies a W/A would be impossible to create.
However, you can, once unlocked, change the secondary profession of your character at will for free. To unlock the Prophecies secondary professions you need to complete a series of medium difficulty quests, to unlock the factions and nightfall secondary professions you pay a guy called senji (found in the early part of factions) 500G for each profession. As i said, once unlocked you can switch between secondary professions at will for free.
For example, i wanted to make a Warrior/Dervish, however i only really like the way prophecies warriors look and also, i wanted to play the story through in order. I first created a Warrior/Elementalist and fought my way through to lions arch where i then caught a boat to Kaineng and found the senji guy, i bought the Dervish secondary profession and then went back to prophecies and continued.
I believe the best starter builds for any warrior is a W/E with a elemental sword and a conjure ability, does insanely high damage in the early levels.