Wondering at Nergal losing to someone who needs Aureola to do more than 12 damage to him in game. And yes, that's using Luce. I don't think anyone gives Lucius anything better than Shine in the DL... which gives him an epic 38HKO (2 damage, folks) against Nergal taken literally. Assuming an average enemy has 10 Res and 45 HP (which might be a little generous?), Lucius would 3HKO them. Even if you scale Nergal down to a third of his HP, he's still soaking up magic like crazy, and 2HKOs with room to spare at 70 Hit.
Lucius, with Shine, is a tad below average on damage against a guy who's only outclassed at magic tanking by freaking Ursula and the Dragon, with lowish HP and evade that isn't all that special.
Now, I think that Nergal over Jill won't be contested too hotly aside from FE10 voters (I might favor Jill there myself), and MOMO has a lot of factors going for her, but I can't stress enough that you pretty much need to see Nergal at under a third PCHP for Lucius to really have a shot.