Rune Knight supposed to be some kind of magic-tank class. Main weapon will be great sword, has limited number of "runes" that can be used for offense (maybe big en-spell effects?) or defense (probably magic damage taken or AoE MDB buff).
I remember literally writing up a description of almost exactly this job back when WoTG was about to come out and everyone was theorizing new classes. Srsly, exactly the same. I was petitioning for the whole 'inbetween pld and drk, is more of a neutral knight, can change between offense/defense, uses greatsword as weapon'.
It sounds fun. I wish I could try it out. But returning to the game at this point would be a massive slap in the face. All my jobs are like 80 at max, all my gear is probably now ****. Is Homam even useful anymore? Not to mention my poor Haub+1, lawl.