I think you have some wrong maths, if i trying count with your base numbers give different results.
For spell power: 2000 with 0/0/61, Empowered Frost Bolt, Ice Shards (200% crits)
Code:
Max DMG Coeficient SP bonus Total DMG Total DMG (Frozen)
IL 255 0,142866667 285,7333333 540,7333333 1622,2
FB 861 0,9143 1828,6 2689,6 2689,6
DMG Time DPS DPS (Both crit)
FB + FB 5379,2 5 1075,84 2151,68
IL + FB 4311,8 4 1077,95 2155,9
IL + IL 3244,4 3 1081,466667 2162,933333
For spell power: 3000 with 0/0/61, Empowered Frost Bolt, Ice Shards (200% crits)
Code:
Max DMG Coeficient SP bonus Total DMG Total DMG (Frozen)
IL 255 0,142866667 428,6 683,6 2050,8
FB 861 0,9143 2742,9 3603,9 3603,9
DMG Time DPS DPS (Both crit)
FB + FB 7207,8 5 1441,56 2883,12
IL + FB 5654,7 4 1413,675 2827,35
IL + IL 4101,6 3 1367,2 2734,4