Lets look closer at Crimson Curse card/ Blood Moon:
You need to sacrifice a unit, preferably a midsized one, to make the effect last many turns... which would be bad on other factions but MO has Deathwish.
Dethlaff Higher Vampire makes it last for 5 turns and immediately comes back, with 2 further charges. Katakan makes it last 6 turns, and still gives you 2x 2pt vampires.
2pt boost on each row, that is 4 pt buffs on each turn, if it lasts 5-6 turns, that is a 20-24 continuous buffs, which is impossible to deny on a vampire dethlaff deck, because they still have the leader charges to create more vampires and the buff effect happens after the bloodmoon player's turn, so if you remove all vampires on that row, he just plays another and gets buffed before its your turn again.
Weather and Yrden seem to be the best counters, or removal/ damage the vampires so the bloodmoon is denied or lasts fewer turns.
But it's still too early to make more than estimates.
(EDIT) I've played a bit more today and i found i might be giving misinformation here: today, when playing against bloodmoon, i saw the buffs happening after my turn, so what i said about the time the buffs take place was probably wrong, i apologize