poison II is the highest damage per mana spent in the game as of now
Bio and BIO II (umbral)does disease DoT and debuffs the mobs damge output
Dia Dia II (astral) does consumes the target from within doing DoT and reducing targets defence.
scourge us umbral and banish is astral
umbral is water/ice/earth
astral is fire/wind/lightening

Since all thm spells are mostly umbral i put all my points into water/ice/earth...although i did get the other 3 to 50 as well