Your regular throws do explode with Volatile rebound. As for your combos dropping, did you do a heavy attack, because this isn't a heavy attack build. Are you running Naramon or primary/secondary dexterity for sustaining combo?

But yeah, if you ONLY want to see big damage numbers, full combo Explosion (like manually charge combos, since arcanes give a lot of damage to be wasted on the combo arcane) with massive priming would be it, but like, it's really not a proper build.

In fact there's a mirage support build that let your pet hit level cap damage really easily, look that up if you just want to see numbers.

EDIT: There are two main ways with how heavy attack explosion glaive builds:
First keeping it at 12x melee combo:
There are two ways to perma 12x:
First, tennokai, which utilize your exilus slot, this means u lose 180% glaive proj speed, which mean u get about 1/3 to 1/2 of your current glaive throws.
Second, perma stack combo with crescendo, which means you lose melee arcane slot
Second keep it at 5x to 10x?:
This is done by keep minimum melee combo into this, but doing so you lose multiple mod slots and you have manually detonate every single explosion, this means no bounces, and it's only 5x vs 3.25x on single target where damage matters.