The calculation of the thoerical max damage that can be done by spells.

So, lets use 890 as the highest damage.

890 * 1.10 = 979, So a fire mage can do 979 damage max on base hit.

Now for the critical and the other spell Curse of Elements.  Based on some tests, Curse of elements can increase the damage of fire by half the amount of fire resistance pushed into the negative in percentage.  The highest curse of elements I know is 75.  So 37.5% damage increase to pyroblast.

979 *1.375 = 1346(approx)
1346 * 1.50(critical damage) = 2019

Now for ignite boost of 40%

2019 * 1.40 = 2836(truncated)

And for the final 268 DoT

2836 + 268 = 3094(truncated)

So a theorical max of 3094 is possible.  Now all we need is the best suit for a full fire mage.  That could increase the damage overall to 3500 or higher.