Maybe I am search challenged but I'm having trouble finding information on what effect having multiple jobs on a character has. I know you can do it, I know it's how you get advanced jobs. But how it actually works is a mystery to me still. I have also found pleanty of posts on leveling up multiple magic or multple war classes for optimization, but nothing about leveling war and magic on the same character.

I have a 14 arcanist that I'm wanting to go scholor with. But I also really enjoy tanking in MMOs and would like an alt to tank with sometimes. Is there any reason I shouldn't just level a tank class on this same character? Does it limit my arcanist, or is literally like having a completely seperate character, stats and all?