Should I attack the hands in rashomon?

No, but they drop items and without them Ibaraki only has 2 attacks per turn

It is recommended to kill them with an AoE NP chained with ST NP. Drops from hands are important which are gourds and sometimes event CEs.

No, you should prioritise on dealing damage to Ibaraki first. You can try to clear them using AoE NPs, otherwise you bully the oni first.

If you're confident on killing Ibaraki, take care of the hands. I usually do this after Ibaraki has about 10k health left and can be killed in 1 turn.

If you have any interest in the gourds then you'll need to kill the hands. If you only care about DP then just kill Ibaraki.