Fenrir.Snick said:
Are it's nasty TP moves instant or could they be stunned with Stun or Headbutt? For that matter, is it resistant to stun at all? It doesn't sound that bad, just a bit of a ***. If it's throat stabga can be stunned than I can't imagine having any problem killing it.
I know this is late, but you can stun most of it's TP moves, but after 5, it will become 95% resistant to stun, in Jupiter's staff and full Dark Magic equipment.
It wasn't a HARD fight, just weird.
Best strategy is to Brick wall and Nuke it. SCH is particularly effective, since Helix generates minimal hate and provides considerable damage. This is one of those rare fights where PLD not engaging is incredibly helpful, limiting it's TP is critical for a smooth fight, Atonement is resisted heavily anyway.
Aside from Interference and Banneret Charge, no TP move was a threat, Kutharei is also susceptible to all debuffs* and He actually stopped using Interference when he gained access to Banneret Charge(33%), if this was just an unlucky fluke, or specific design, I can't say.
*Saboteur'd Addle + Barspell (Barfire primarily) are a great combo, as most of it's spells can be resisted at that point.
Ignore the idiots on Wikipedia, nuking his elemental affinity and assuming it resists magic heavily. Thunder IV and Ionohelix landed with no more than a 15% damage reduction, which is perfectly reasonable for an NM of this nature.