Ok, so I pulled 70% and 25% out of my rear. Let's find out where they are, actually.
Let's compare Shout (lvl4) and Cone of Cold (lvl 5) and Fireball (lvl3). This isn't the only way to compare, but it may shed some light on the issue:
Shout: Emits an ear-splitting yell that does 1d3+3 sonic damage per caster level to a max of 15d3+45 at level 15 to all targets in its path. A successful Fortitude save halves the damage.
Cone of Cold: Cone of cold creates an area of extreme cold, originating at your hand and extending outward in a large cone. It drains heat, dealing 1d6+5 points of cold damage per caster level. Maximum damage 15d6+75 at caster level 15. A successful Reflex save reduces the damage by half.
Fireball: Creates a ball of fire that detonates on impact, causing an explosion of flame that deals 1d6+3 points of fire damage per caster level up to a maximum damage of 10d6+30 at caster level 10 to all targets around it.
Let's assume Pure Casters, Empower, Maximize, Intensify, and close to max spell power. Bursting damage with Wellspring of Power. I've already done a Fire SP breakdown elsewhere (
https://www.ddo.com/forums/showthrea...wer?highlight=)
Let's take ~1500 as a burst damage spell power for end-game fire and cold sorcs.
From that number, we can subtract 6 (equipment), 55 cores and elemental form vs SS capstone, 65 other enh, 29 insight on equip, 202 RL belt, 60 destiny stuff, 66 filigree, and 20 other tree enh avail to sorcs
So a SS Bard can get about ~1000 max sonic spell power
Let's talk CASTER LEVELS
Fireball MCL 20 (with feat)
Cone of Cold MCL 19 with ENH
SONIC MCL 15 (can't find a way to surpass this on bard. Let me know)
FIRE SORC 20(CL)*16(sp 100base+1500)*6.5 (avg dmg dice)=2080
ICE SORC 19*16*8.5=2584
SS BARD: 15*11*5=825
BARD to FIRE: 39.6%
BARD to COLD: 31.93%
This is before crits.. It gets quite a bit worse. I'll skip that, and say that my ballpark of Bards doing about 25% of Sorcs is correct.