While engaging a NM, Siphon MP is not enough (trust me I know from experience). With the new party sizes that will be implemented in the new patch MP regen will be needed. Once they fix the Ancient Spells mages will burn through their MP, considering you have to pump it up with regular spells (for Flood use water based spells prior to timer going off). I have been waiting for MP Regen since I started back in October, and this is one thing they will not get rid of.