I found Lucas' charm is in armor and blocking (mostly blocking, but items usually have + for both). I've done two hardcore playthroughs with him (in the demo, natch), got some warding/retribution/stagger items and hilarity ensued. Vera couldn't damage me, I was just standing there, she could do whatever she wanted, not even my focus drained.
Sure, you have a bit lower attack and agility, but the biggest problem with DMC4 too was that enemies died too fast IMO, so that's fine by me.
BTW, can retribution crit? Vera had like ~60 hp left, but 1 19 damage retri suddenly killed her (couldn't see the damage floater 'cause the camera was zoomed in).