Feinting isn't ineffective in battle, noone expects you to feint in battle since theres so much going around you and it's so fast paced (unless you fight a decent player), I assume thats why I get most of my kills. In terms of dueling, if you are bad at feinting it is a hinderence. However, you get some excellent feinters, if I were you I would spectate some good duelists and then duel them- In my opinion, the only way to learn is getting your ass handed to you many many many times.
Also I agree, Native duelists (Nditions guys) are much greater than cRPG duelists in terms of feinting (which is relevant to the OP- feinting). You see some of the best dueling there, especially since there is no armour crutching and one sword fits all. You should train there, in fact everyone should train there!