I find him easy, i always go for an all out attack, Zidane,Steiner,Freya and Amarant, i usally kill him before he get's me. If you.ve got Auto-Regen on you don't need a healer. If Necron casts Doom on someone, use a pheonix down on em. Also make sure you've got the best weapons/armour on everyone.
I have the best I can on everybody. But he still beats me to scrap.
I have auto-regen, and is useless. It heals way to less. NEcron is hard and unbelievably stupid. Kuja should've been the Final Boss.