I hate that mission. You need luck, a s**t lot of pheonix downs, a safety bit, and heavenly DMW... good dodging skills too. this may be asking a lot. i would recomend that you leave this mission for a while.

im level 57, 30,000+ hp, 97 atk good vit, and i found it hard.

Also, if you're trying to complete 100% mission, do as many as you can in the chapter where you make the flower wagon for aerith. (the woman in the front of the shinra building gives you free raise efects!!)