Cecilia: Horse Emblem Debuffer

Hi everyone. While I wait to obtain more Feathers and SP to teach my Cecilia the cav buffs that will make her much more powerful on my Horse Emblem team (I'm thinking either Hone or Goad), I have as her C skill Threaten Res 3. Is this a good enough skill that would help her deal with mages my other allies would otherwise struggle against? I have Legendary Ephraim and Ares on my team - both known for their extreme weakness to magic.