Would like to see fusion bolt even finish charging by the time room is dead with act 7, crash shot, wm, or shooting rush. And then you have either low damage aoe or decent single target damage that drops off. I'm not a huge fan of it. I'd love to see some videos of this deadly fusion bolt in action, especially in harder content.
Come zero, it's going to charge faster at the price of apm and vulnerability to screwing up. And even then, firebolt's going to hit much harder.
In current game one can get around 1260 intelligence, 20 magic attack from enchants, 10 from scathach title, 20 from the wand, for a total of 113. Also included is r1 bolt mastery (15%), r1 fusion bolt (15%), r1 elemental masteries (15%), r1 magic mastery (10%), magic attack title (5%), wand upgrades (+21%), special upgrades (21%), hebona set (10%), bolt mastery 20 headgear reforge (20%)
The formula for bolts is the same as intermediate magics, it would be applied as:
150 * 1.21 * (1 + 1.13 + 0.15 + 0.15 + 0.2) * 1.1 * 1.26 = 661 for lightning bolt
120 * 1.21 * (1 + 1.13 + 0.15 + 0.15 + 0.1 + 0.2) * 1.1 * 1.26 = 579 for firebolt
80 * 1.21 * (1 + 1.13 + 0.15 + 0.15 + 0.1 + 0.2) * 1.1 * 1.26 = 366 for icebolt
This is of course, ignoring that bolts only receive damage from special upgrades if you are using the wand of the same type and ignoring bonus stats from any possible max damage from enchants or wand type. For ease of calculation, it should come out similarly enough.
Starting with fire - ice, because it is the most notable fusion:
Last Four Bolts: [579 * (4 + 3 + 2 + 1) + 366 * (1 + 1 + 1 + 1)] * 1.15 = 8342
First of Five: [579 * 5 + 366] * 1.3 * 1.15 = 4875
TOTAL = 13217
So yes, in current game standards its pretty much crap. Now pretend we are fully updated like KR. Lets just say you have 500 magic attack with your staff and you want to throw out some fusion bolts to kill stragglers.
[150 + (500 * 0.6)] * (1 + 2.5 + 0.15 + 0.15 + 0.2) = 1800 lightning bolt damage
[120 + (500 * 0.5)] * (1 + 2.5 + 0.15 + 0.15 + 0.1 + 0.2) = 1517 firebolt damage
[80 + (500 * 0.4)] * (1 + 2.5 + 0.15 + 0.15 + 0.1 + 0.2) = 1148 icebolt damage
Well firebolt damage would be a straight 1517 * 6.5 = 9860, so that should make it obvious that fusion bolt is inferior from the start. But how does fire - ice hold up:
Last Four Bolts: [1517 * (4 + 3 + 2 + 1) + 1148 * (1 + 1 + 1 + 1)] * 1.15 = 22726
First of Five: [1517 * 5 + 1148] * 1.3 * 1.15 = 13055
TOTAL = 35781
It starts to become an asset. Perhaps not quite the same punch as firebolt spam, but still fair damage.