lol, after reading your post twice, I still missed the Elements Set! 
only Crushing Flames affects the damage of Crushing Blow. the +100% Damage will increase the damage of any Skill/Proc that causes MH Damage.
if you have 100 points in Power and +25% Item Quality on a level 100 Dagger with +100% WD, your Weapon Damage is 28,500. I guess you have Quick Attack & Blinkstrike 20?
Quick Attack: 28.5k x 2 (20 Skill Points) x 1.875 (7 Shock Effects) x 1.5 (Ruptured and Bleeding enemies) x 4.5 (Electrification when enemy HP at 25% or lower) x Attack Speed (for damage per second).
Blinkstrike: (28.5k x 5 (Blinkstrike does 500% MH dmg)) x 2 (20 Skill Points) x 1.875 x 1.5 x 4.5 x Cool Down (for damage per second).
Orb: 28.5k x 2 (Orb does 200% MH dmg) x 1.875 x 1.5 x 4.5 x 10 (Orb has 10 Attacks per Second). 25% to Proc when CD is finished.
Bleed: does 100% of the attacks damage that caused Bleed every second for 10 seconds. Bleed has the same chance as all other attacks to cause Crushing Blow.
Critical Hit: all of your attacks, including Bleed (but not Crushing Blow) have a 10% chance to do x 1.5 Critical Damage.
Quick Attack & Blinkstrike get x 1.3 from Mutilate Talent.
when Crushing Blow/Flames gets your enemies Health down to 25%, all attacks get x 1.375 from Relentless Talent. that 1.375 goes up as your enemies Health gets lower. of course, the multiplier is lower when the enemies Health is higher.
Crushing Blow: gives a chance to do 25% of your enemies current Health in damage. CB is not affected by any other damage modifier except for Crushing Flames. I don’t believe that CB can cause Bleed (at least not that I have heard of or read on the Forums).
I read in an old post, a Developer said that Crushing Blow is a different type of damage attack that directly reduces enemy health but is not affected by other damage modifiers. just think, a Critical Hit with +350 Critical Damage, on a Crushing Blow when you first hit an enemy could kill it with one hit (except for higher Tier monsters). with Crushing Flames, only Legend & Mythic Monsters couldn’t be one hit dead, not sure of the Epic monsters. ahh, I found the post.
there are a lot of posts and threads about Crushing Blow if you want more information about it.