Push the Limit affix can increase damage by 18% for legend gear and up to 36% on eternal gears. This affix increases the cost of what you cast. PTL can be obtained from drop only.
Barbarian can increase damage by 18% for legend gear and up to 36% on eternal gears. This affix increases dmg but reduces your MP. Barbarian can be obtained from drop only.
Glass cannon increases damage and reduces HP by 18% for legend gear and up to 36% on eternal gears. Glass cannon can be obtained via Ruby or Drop.
Energy increase damage by % missing MP.
Fury increases damage of specials by MP remaining.
Have a read on my friends guide below for Damage maximizing.