Hemostasis just does not work most of the time with Masochistic Tendencies. I just watch my monsters die as they cast multiple spells in a turn, killing themselves, even though they’re only supposed to be able to take damage once per turn. Sometimes it works- most of the time, no.
Katarina’s Return also does not ever seem to work with Masochistic Tendencies, as my creatures are certainly not healing up after damaging themselves.
My creatures use the “cast on healing” spell gems properties, in case that might be related.
This happens before my creatures hit the “healing cap” per turn, just to mention that.