This [Redeemer Prime] build is only to be used as a stat stick, for combo, and for status application. It does not do much damage, and is not built to be a damage dealer, let me get that out of the way first.

to quote the wiki:

"The Melee combo counter will increment by 5 for each enemy hit by the shotgun blast, regardless of how many pellets actually connect with each target. Hitting multiple targets via shotgun spread or punch through will increment the counter by five times the number of enemies hit.
[True Punishment] synergizes very well with this, doubling the combo counter amount granted by each hit. (Though, it is currently bugged to do 4x the base combo, resulting in 20 combo per enemy hit instead of the supposed 10.)"

The [Redeemer Prime] is currently the best way to get max combo fast in the game, which is why i use this with my [Ash] bladestorm build. The [High Noon] stance works insanely well with this, allowing for an only fire playstyle, where you use the first hit of the forward combo, and the first hit of the standing combo in succession. you will stay in place, and perform only blasts, to gain maximum combo in the least amount of time.

[Blood Rush] allows for crits, which will proc Arcane [Fury], and grant a buff to this, and [Ash]'s bladestorm. [Lasting Sting] for the viral procs to last longer, [Weeping Wounds] to proc (Because you'll always be at 12x combo, if you're not, you'll get there in less than 3 seconds.), and true punishment for combo gain, The 60-60 mods can be swapped out for the 90 mods if you want a more guaranteed viral proc, however you'll lose some status chance.

[Drifting Contact] is a personal preference, as at the rate you gain combo, it's no big deal to lose all your combo. you may swap [Primed Fury] out for either berserker, or normal [Fury], though i find berserker too fast, and it doesn't apply to [Ash]'s bladestorm.