Just killed Keriax - it was something that needed to be done and I felt confident enough in my abilities. Started by equipping Orb of +10 Wis, coupled with two boost wisdom potions. Threw a potion of invis at him which I guess made him invis (I could still see though - thought it was supposed to confuse him?), followed by throwing potion of blindness at him. I then proceeded to melee him and it took 4 or 5 turns - he got some hits on me while staggering around, but he dropped very nicely to my sword.
As for the wish I agree it seems unnecessary - I have concentration so it's likely I'll choose PoGA a bit later.