Need a quick drg combo lesson

So i'm fooling around on my Drg and trying to use the B4B>Heavy Thrust>Power Surge>Life Surge>Jump combo. I was doing it pretty well so I tried modifying it a bit. I came up with B4B>Heavy Thrust>Power Surge>Impulse Drive>Disembowel>Life Surge>Jump. Problem here; apparently Drg can't combo Impulse Drive and Disembowel. Is this True? I grabbed a few mobs and only spammed the two and never got a sinlge combo. The reason I wanted to add this combo is for the extra piercing dmg you'd get. Any help would be greatly appreciated. Am I right that you cant combo these on Drg?

Thanks for your help!

In order to combo Impulse Drive > Disembowel you need to do the Impulse Drive from behind the target, only this way you will be able to combo Disembowel and get it's debuff on the mob.

Second, when you do the Full Thrust combo your Full Thrust has 300 potency. Do your combo until you reach Full Thrust, then B4B > Life Surge > Full Thrust. I tried to buff my Jumps with B4B, Power Life Surge, Life Surge but noted that i will never reach the damage of my Full Thrust Combo with this. Highest Crit would be 868 on ?? Boss Mobs in 50er Dungeons. With Jump you will do around 800+

I do jump with internal release crit buff + the leftover from B4B.

What i normaly do is this (Mostly for Boss Fights, because Trash is ... just Trash and dies too fast ^^):
-Do the Chaos Thrust Combo for Piercing Resist down + DOT
-Do Phetobomize for DOT (?)
-Do Heavy Thrust for DMG Buff
-Start Full Thrust Combo, B4B, Life Surge, Full Thrust
-Do the Full Thrust Combo as long as DOTS/Debuffs/Buffs tick
-Internal Release Jump

But note that you have to adapt on the situation rather than stick to a combo setup.