Monsters have no set MATK, if it is ever used (by skills, for example) it uses the MATK Formula, which depends if you're on Renewal or Pre-Renewal. So, basically, for MATK, only INT is necessary. Monsters also, have no set HIT, which is calculated by it's own formula, which also depends on if you're on Pre or Renewal, but, usually, DEX and BaseLevel are the catalysts. By the way, monsters DO have preset ATK, min and max, but it's directly affected by it's own Strength. On doc/mob_db.txt lays a brief explanation of each stats purpose.
STR: Strength of the monster. Affects ATK.
AGI: Agility of the monster. Affects FLEE.
VIT: Vitality of the monster. Adds additional DEF.
INT: Intelligence of the monster. Adds additional MATK.
DEX: Dexterity of the monster. Affects HIT rate.
LUK: Luck of the monster. Affects Perfect dodge/Lucky flee/Perfect flee/Lucky dodge rate.