these are probably the a3 merc stats:
fireball is already at level 29 or so. levels should not be ramped up too high, because +skill items matter less then (given the enddamage is the same). The damage is borderline to useful/uselesss. With a mastery set at a flat endlevel of level 1 (level 12 with gear, no level scaling) it would already look really good. A level 20 (31 with gear) would be a too much i think. Gear is Ormus (With Amethyst for Shield), Hexfire (Facet)/Spirit, Spirit Shield, Flickering Flame/ Griffons (Facet)/ Nightwing (Facet).
For Fire (lvl 98): they probably raised Enchant to level 20, like most secondary skills are
firebolt (lvl 20): 306-407
fireball (lvl 29): 1614-1783
enchant (lvl 20): 84-110 Fire Damage, +191% AR, 600 seconds
with +11 gear:
firebolt (lvl 31): 1307-1488 (1568-1786 with +Fire Dmg; -15%res not applied yet)
fireball (lvl 40): 2591-2811 (3110-3373 with +Fire Dmg; -15%res not applied yet)
enchant (lvl 31): 176-214 Fire Damage (211-257 with +Fire Damage), +290% AR, 864 seconds
with mastery (lvl 1) and +11 gear:
firebolt (lvl 31): 2200-2504 (2640-3005 with +Fire Dmg; -15%res not applied yet)
fireball (lvl 40): 4361-4731 (5233-5677 with +Fire Dmg; -15%res not applied yet)
enchant (lvl 31): 316-382 Fire Damage (379-458 with +Fire Damage), +290% AR, 864 seconds
fire mastery (lvl 12): 107%
with mastery (lvl20) and +11 gear:
firebolt (lvl 31): 3614-4113 (4337-4936 with +Fire Dmg; -15%res not applied yet)
fireball (lvl 40): 7164-7771 (8596-9325 with +Fire Dmg; -15%res not applied yet)
enchant (lvl 31): 520-629 Fire Damage, +290% AR, 864 seconds
fire mastery (lvl 31): 240%
For Cold: lvl 98 they probably raised glacial spike to level 29 like fireball and lightning are (from level 9)
ice bolt (lvl 20): 253-266, 26.5 sec frozen
glacial spike (lvl 28): 718-762, 5.3 sec frozen
frozen armor (lvl 16 now, lvl 20 used here): +125% defense, freezes for 3,4 secs, 348 sec Duration
with +9 gear:
ice bolt (lvl 29): 498-516, 33,5 secs frozen (672-697 with +Cold Dmg from gear)
glacial spike (lvl 38): 1006-1059, 6,4 secs frozen (1358-1430 with +Cold Dmg from gear)
frozen armor (lvl 29): +170% defense,4.5 secs frozen, 456 sec Duration
For Lightning: lvl 98 they probably raised bolt level to 20 (from 12), static i just use level 20 like the other secondary skills)
charged Bolt (lvl 20): 49-57, 22 bolts
lightning level (lvl 29): 1-1851
static (lvl 20): 16 yards (yards comparison: https://www.theamazonbasin.com/wiki/images/a/a4/Radius.png)
with +8 gear:
charged Bolt (lvl 28): 90-98, 24 bolts (122-132 with +Lgt Dmg, -20%res not applied yet)
lightning level (lvl 37): 1-2884 (1-3893 with +Lgt Dmg, -20%res not applied yet)
static (lvl 28): 21.3 yards
with mastery (lvl 1) and +8 gear:
charged Bolt (lvl 28): 161-174, 24 bolts
lightning level (lvl 37): 2-5142 (3-6942 with +Lgt Dmg, -20%res not applied yet)
static (lvl 28): 21.3 yards
mastery (lvl 9): +146%
with mastery (lvl 20) and +8 gear:
charged Bolt (lvl 28): 380-407, 24 bolts
lightning level (lvl 37): 4-9908 (5-13376 with +Lgt Dmg, -20%res not applied yet)
static (lvl 28): 21.3 yards
mastery (lvl 28): +374%