Honestly, I wouldn't say Yaldabaoth is that hard of a boss. If you're within level 70, the boss should go down without a problem. You'll have enough HP to survive his more damaging attacks, and your damage will be high enough to quickly put down his arms. The real problem of Yaldabaoth is how long his fight is. Bring all the SP items you can find, and be sure to heal at Lavenza before you take on the boss.