I haven't started my Rift Mage yet, but let's try to do some math (I'm not 100% comfortable doing math for a game whose mechanics I'm not sure about, but I'll give it a shot). I'll start with Fire.
The relevant spells and abilities:
Fire Mine
Fire Damage:1,600% weapon damage
Activation Delay: 3 seconds
Cooldown Time: 24 seconds
Cost: 35 mana
Searing Glyph
Burning: 200% weapon damage per second
Burning Duration: 8 seconds
Pyromancer
Burning Duration Bonus: 25%
Fear Duration Bonus: 25%
Willpower on Unlock: +3
So a single use of Fire Mine (Searing Glyph) = 1600 + (200 * (8 * 1.25)) = 3600% weapon damage
Now for Storm:
Energy Barrage
Projectiles: 12
Damage per Hit: 66% weapon damage
Cooldown Time: 16 seconds
Cost: 50 mana
Energy Bombardment
Magic Resistance: -2% (for each projectile hit)
Static Cage
Duration: 8 seconds
Area of Effect: 9 meters
Paralyzed Duration: 2 seconds
Cooldown Time: 32 seconds
Cost: 65 mana
Lightning Cage
Electric Damage: 50% weapon damage (for each projectile hit)
Taking into account the resistance debuff of Energy Bombardment isn't too difficult, though I have to make some assumptions. First, I'll assume that 1% magic resistance equals 1% less damage taken, so -1% means 1% more damage taken. Second, I'll assume that the debuff from Energy Bombardment applies before the damage from Lightning Cage. Finally, I'll assume that the staff type you're using is Lightning, because Lightning Cage does deal lightning damage (and not staff damage, as Energy Barrage does).
So a single use of Static Cage -> Energy Barrage =
Sum [66 * (1 + (.02 * (N - 1))) + 50 * (1 + (.02 * N))]
from N = 0 to N = 12
I get about 1557% weapon damage.
Now, Energy Barrage is on a 16 second cooldown, whereas Fire Mine is on a 24 second cooldown, but Static Cage is on a 32 second cooldown. So you'll be having to cast a "regular" Energy Barrage about half the time. Energy Barrage alone does:
Sum [66 * (1 + (.02 * (N - 1)))]
from N = 0 to N = 12
= 879% weapon damage
Fire Mine = 3600% / 24 seconds = 150% weapon damage per second
Energy Barrage + Static Cage = (1557% + 879%) / 32 = 76% weapon damage per second
Fire Mine is also way more mana efficient, if that matters for a Rift Mage.
Unless I'm missing something, which could be likely.