Currently lvl 34 while following the grinding guide, just reset my stats, chose Daring, put everything into DEX (60 now) and the rest in POW. (10 now)
Problem is, my strongest weapon is a Balmung +10 with about 300 power now, which gives me about 2000 attack with magatamas counted, and I can't solo Yakumo. Even not normal. Beelzebub just 3-4 shots me.

Anyone got some advice for me?
PS: Posting here because the general discussion board is spammed with spam. :/

+10 is the problem.

Go get it to the upper limit of what's possible for you at the moment. The grinding guide is made under the assumption that you're at least keeping up with your gear to some extent.

SupremeTentacle wrote:+10 is the problem.

This, and it's probably better to go bow. Other than that, just spam yakumo until you get it. With bow, you can keep your distance and close in on it to shoot after it charges and can also shoot as it takes off. Bow also has a good advantage at around kyoto vs ts because of the level 41 red bow with +5 dex (failnaught). Well, you can always equip ts magatama and bow beelzebub and it'd still be faster, probably. To stop being one shotted, I think you'd need to equip the amber magatama @41 iirc.