6/5/26 Update
Adjusted the build to include a Pet from Beast Master after the Chapter 6 update.

Made some significant changes to the original Rifleman/Assassin Build that improves defenses a bit more along with providing a pet. Almost identical but the suggestions provided in the Original Guide are being posted here. You get roughly 3 additional defense across the board when you have a fully Bio Engineered Pet.

Overview:
Long Range Damage, Damage Boost for group PVP.
Stay in the back in PVP as you cannot take many hits.
Damage increases the longer you hit targets by stacking Ambush (Armor Neglect (same as Riddle Armor from commando but better cooldown) 5x=10-15% estimation), Resonance (Armor Neglect 3x=6%), Savagery (Critical Hit Damage 3x=15%), Blaster Burst (Damage Increase 5x=10%), add Second Fire proc chance, Assassins Mark proc chance, add Cold Element Proc (72x0.2=14.40% Damage Increase). Once everything is stacked High HP mobs start to melt.

Content Solo:
Sher Kar - YES (6-11k DPS w/ Damage PuPs and Damage Stance)
Revanite Daily - YES (w/ Tank Stance and a Enfeeble Pet)
Hracca Daily - YES (Boss - YES w/ Tank Stance and a Enfeeble Pet, wear Steel Body Jewelry, may need to use Defense Cooldowns such as Void Walk and Decoy)

Pro:
Great PVE clear speed at long range.
Provides armor penetration, and increased damage to group PVP.
Just enough defense for PVE.
BOOST DEFENSE FURTHER WITH STEEL BODY JEWELRY SET.

Con:
Very few cooldown defenses for PVP

Expertise:

Marksman: With the 4.9 Update defenses have shifted more toward Block but noticed Dodge was little lower then I prefer to obtained Dodge, Fanshot has nice cone AoE damage but is limited at present 45m.

Rifleman: We want attacks Focused Fire, Ambush (Armor Neglect stack 5x), Sweeping Fire is a very narrow Cone attack that doesn't do much damage so maybe place the point somewhere else if you want.

Assassin: We want more Attacks and Damage, Blaster Burst (Razor Slash) stacks 5x, Assassinate. Decoy provides a few seconds of no damage taken, roughly 3-5 hits, which is great for PVP. Flash Bang has 30m range very nice AoE Stun (prevents player from using ablities), and Ambush/Snipe (DoT damage with reduction to heal potency), two great abilities for PVP. Avoid Damage has a negative debuff and should be avoided.
(Drop Master Assassin and use it in Teras Kasi to get Master Teras Kasi to wear Steel Body Jewelry Set to be more defensive)

Doctor: Lost alot of Doctor with the Chapter 6 update, as we need more points in Beast Master.

Teras Kasi Artist: Teras Kasi Artist provides the best increase to Block. Steel Body Jewelry set provides some of the best well rounded defense in the game.

Beast Mastery: Chapter 6 now requires 17 Points to remove the -25% Damage Output Debuff obtained at Master. Bio Engineered pets can provide 3-3.5% more defenses across the board. Recommend a pet that has Enfeeble to provide a debuff to targets reducing there damage output by 20%, giving the build much more Tanking ability. Beast Empathy is beneficial early on for a pet to keep them happy and progressing to Best Friend Forever, once the pet is BFF transition to Enhanced Skill Acquisition to obtain needed skills such as Enfeeble and train the pet.

Preferred Buffs and Gear:
Usual Stacked Buffs - Doctor, Squad Leader, Junk Dealer, Favor of the Elders, Tactical Stim, Lasting Performance, Familiar, Mustafar Injector.
Entertainer Inspiration - 3000 Kinetic, 3000 Energy, 6% Second Chance Heal, 5% Evasion, 240 Luck.
Jewelry Set - Razor Cat (Damage), Steel Body (Tank)
Attachments - 4 Piece Luck, Stamina, Block Value. 4 Piece Luck, Constitution, Block Value.
Attachments (Alternative for more damage) - 8 Piece Luck, Precision, Strength.
Exotics - Critical Hit Reduction, Healing Potency, Weapon Damage Increase.
Exotics (Alternative for more damage) - Weapon Damage Increase, Rifle Damage Increase, Luck.
Powerups - 3 Weapon Damage Increase.

Final Notes:
Do pay attention to the suggestion to use Steel Body, it makes the build alot more tanky.
Does well for Weapon Swap in Exar Kun, not as damaging as the previous version of the build since it loses the proc chance from commando, but this one is more tanky.