I think you are quibbling over relatively irrelevant amounts of damage.
I think you will be down a x2.25 damage multiplier due to lacking helpless on most mobs, down to a x1.25 multiplier on crits using highest durable available staves as you level instead of x1.7 multiplier with elemental bloom due to lacking stacked item defense, and down to x1.5 stat damage with dex instead of x2 stat damage from falconry with deadly instinct.
The net result is that if you have 50 base damage, and a 24 stat modifier by end of heroics:
Your dex build will multiply that 24 dex modifier by 1.5 to get 36 damage from dex, then add 50 base damage to get 86 base damage. Then it will multiply that by 1.25 for crit, and hit for 108 per hit by end of heroics (before melee power).
Heroic Soundburst Staffy will multiply that 24 wisdom modifier by 2 to get 48 damage from wisdom, then add 50 base damage to get 98. Then it will multiply that by 1.7 for crit, then multiply it again on most mobs by 2.25 for helpless, and hit most mobs for 375 by end of heroics, plus enable another 40 sneak damage due to helpless, and end up hitting for around 415 per hit by end of heroics (before melee power).
Wether or not 108 damage per hit by the end of heroics has more doublestrike or glancing blow damage is ... relatively irrelevant when you are already giving up 300 damage per hit (before melee power). The person in the group that doesn't give up 3/4ths of their damage like the pure sorc or warlock will end up killing most of the dungeon, and you will end up piking regardless.
This is also why people say cleaves aren't good on staff builds. If you are piking, then AoE piking with cleaves don't matter. But if you are annihilating things, then AoE annihilating things with cleaves is good times. People say cleaves with handwraps are terrible too, but when handwraps annihilate on hit in a similiar build,
handwrap cleaves annihilate as well. Staff cleaves are way better than handwrap cleaves.