BTW, been fiddlign with cheatengine, and managed to get my first 3 recruits up to assassin rank in just a few mintues. view their current xp from the guild panel, search for the value as 4byte integer, then use the assainate ability on a group of enemies, once they get back to base, filter the new results, after another filter you'll get 2 results per assasin. Set the values to 90(10 xp less than needed) then send them to assasinte again, and they will level up.
As soon as they vacate the map, set their xp to 90 again, and they will be ready to level up again after an assasination. You maybe able to set their xp to say 1090 so one go will get to assassin, but havnt tried this, and it may mess them up, so i wouldnt recommend that.
So after 10 mins or so i now have 3 rank 11 assassins, which is awesome.