Technically, they have Mantle and not Nihil lol, but Mantle's basically an auto-Nihil.
Huh? On Easy, I couldn't manage that... Not without everyone taking a lot of damage from counters. >_>
That's why you use a Fortify staff, because it cuts the 10 or so turns it takes to beat the chapter to about three. And elements in normal mode will also be your downfall if your units can't evade very well, or have low resistance; those were among the many factors as to why I couldn't beat FE10 on normal mode my first time through.