The addition of Primary Merciless was a much needed buff to many primaries.
This arcane helps mostly the stronger weapons though and those that deal AoE and DoT (sadly this seems to be quite common from DE).
[Amprex] checks both tick boxes really well making it even better to clear SP mobs.

Again lets make the most out of this:
96% CC * 30% HM = 28.8% Bleed proc
16.2 FR reaching a max of 3.3 MS = 53.46 shots per sec
This means we have an average of 15 bleed procs per sec on every single target!
This is a Chain Gun, each chain has 10m.

I got your attention yet? :P

Main Viral buffs Bleed DoT
Electric provides much needed crowd control on Steel Path while also removing shields that resist your Bleed procs on current WF.

I decided to run Sinister Reach because new maps seem to be more open which is a drawback to Amprex reduced main beam range, 18m -> 30m.

Sadly this build doesn't have much flexibility, but then again it doesn't need to because it can deal with anything.

Rivens

I'm still in disbelief when [Amprex] dispo is this low comparing with melees. Both are short range AoE.
But then we currently have [Glaive Prime] with a better dispo than [Amprex], which without riven 1 shots SP mobs from a far and 2 shots acolytes.

Even so, if you have an [Amprex] riven with +CD +CC along with something that we needed it will have room.
If you're lucky to get Toxin along swap out [Malignant Force].
if it's Cold, [Primed Cryo Rounds].
If you get FR swap out [Primed Shred].
If it's damage, [Serration]... (even if currently the +dmg is lower)

Not much we can do, all the mods are essential, so we depend a lot on riven dispo and it's stats.

If you get a riven with CC there's another change you should do, swap Critical Delay for Point Strike, above 100% we don't need the CC with the FR handicap.

Have fun