https://www.icy-veins.com/d3/follower-skills-and-gearing-guide

https://www.icy-veins.com/d3/templar-follower-skills-and-gearing-guide

The recommended abilities for the Scoundrel are:
Level 5: It is important to note that hard crowd control from skills is something your build might want to avoid — either because it prefers to control the fights itself and CC might hamper that, or simply from speed farming considerations. In such a case, do NOT select a first skill, as there is no way to unlearn it and you will have to re-level a new character simply to get a “fresh” Scoundrel to accompany you. Otherwise, we recommend Powered Shot — a hard crowd control ability that can save your life and offer you a moment of respite every 8 seconds, topped off with a Dexterity-scaling duration.
Level 10: Anatomy — a passive buff to Critical Hit Chance that scales with Dexterity on your follower equipment.
Level 15: Piercing Shot — a boilerplate 10% damage buff against enemies affected by this skill; once again, its piercing properties lend themselves well to character builds that displace enemies into clumps.
Level 20: Night's Veil — the highlight of the Scoundrel abilities, this circular AoE effect covers a decent 20 yard area and guarantees critical hits against enemies caught inside. Needless to say, this is a massive damage boon whose duration scales with Dexterity, and is the prime reason to take the Scoundrel.

Scoundrel Setup - Solo GR Pushing
The following setup reflects the best-in-slot item choices and gear rolls for a Scoundrel taken to Greater Rifts with the intent of pushing leaderboard. Note that you can either focus on Crowd Control with the inclusion of Blind Faith, Cord of the Sherma and Cluckeye in the setup, or do a straightforward “buffing” Scoundrel with Leoric's Crown, String of Ears, and a generic bow or crossbow. Tal Rasha's Relentless Pursuit is included due to its innate Increased Attack Speed roll, but is not a necessary part of the setup.

Templar Skills

Level 5: Heal Heal — The highlight of Templar abilities, his healing scales with Strength on gear and is uniquely affected by cooldown reduction on gear. Its decent base 30 second cooldown can be cut down by more than half with enough Cooldown Reduction investment, and can be attractive to fragile builds with low sustain — i.e. Demon Hunter Cluster Arrow variants.
Level 10: Loyalty Loyalty — a source of Life Regeneration that also scales based on the Templar's Strength, this skill is another decent boon to low sustain character builds and attains additional for setups that include Molten Wildebeest's Gizzard Molten Wildebeest's Gizzard.
Level 15: Onslaught Onslaught — on a decent 20 second cooldown, the Templar can boost you with a 10% damage increase against enemies affected by this skill, again — with a Strength-scaling duration.
Level 20: Guardian Guardian — this skill offers you a cheat death alternative (or addition) to the one present in your character passive skill lineup. For most builds, this allows you to drop your own cheat death passive slot during GR progression.

3. Templar Setup - Solo GR Pushing
The following setup reflects the best-in-slot item choices and gear rolls for a Templar taken to Greater Rifts with the intent of pushing leaderboard. Note the focus on Cooldown Reduction with the inclusion of the craftable Cpt. Crimson set, since the Templar can take advantage of CDR on gear for his Heal Heal. Tal Rasha's Relentless Pursuit Tal Rasha's Relentless Pursuit is included due to its innate Increased Attack Speed roll, but is not a necessary part of the setup. The Gloves of Worship Gloves of Worship are included to make the build semi-viable for standard rift farming and bounties as well, though we do not recommend the Templar for the purpose; there simply is not a great option for the slot otherwise.

Slot Pieces Stat Priority
Head
Leoric's Crown Leoric's Crown
Strength
Socket (Diamond)
Critical Hit Chance
Vitality
Crowd Control Reduction (Secondary Stat)
Physical or Lightning Resistance (Secondary Stat)
Shoulders
Homing Pads Homing Pads
Strength
Cooldown Reduction
Vitality
Life % or All Resistance
Pickup Radius (Secondary Stat)
Health Globe Healing Bonus (Secondary Stat)
Torso
Tal Rasha's Relentless Pursuit Tal Rasha's Relentless Pursuit
Strength
Attack Speed (if Tal's chest)
3 Sockets (Rubies)
Vitality
All Resistance
Melee or Missile Damage Reduction (Secondary Stat)
Physical or Lightning Resistance (Secondary Stat)
Wrists
Nemesis Bracers Nemesis Bracers
Strength
Critical Hit Chance
Vitality
All Resistance
Melee or Missile Damage Reduction (Secondary Stat)
Hands
Gloves of Worship Gloves of Worship
Strength
Cooldown Reduction
Increased Attack Speed
Life on Hit
Physical or Lightning Resistance (Secondary Stat)
Pickup Radius (Secondary Stat)
Waist
Captain Crimson's Silk Girdle Captain Crimson's Silk Girdle
Strength
Cooldown Reduction
Vitality
All Resistance
Life per Kill (Secondary Stat)
Legs
Captain Crimson's Thrust Captain Crimson's Thrust
Strength
2 Sockets (Rubies)
Vitality
All Resistance
Life per Kill (Secondary Stat)
Physical or Lightning Resistance (Secondary Stat)
Feet
Ice Climbers Ice Climbers
Strength
Vitality
All Resistance
Armor
Pickup Radius (Secondary Stat)
Health Globe Healing Bonus (Secondary Stat)
Amulet
The Flavor of Time The Flavor of Time
Strength
Socket (Ruby)
Cooldown Reduction
Increased Attack Speed
Melee or Missile Damage Reduction (Secondary Stat)
Ring #1
Unity Unity
Strength
Socket (Ruby)
Cooldown Reduction
Increased Attack Speed
Life on Hit
Ring #2
Oculus Ring Oculus Ring
Strength
Socket (Ruby)
Cooldown Reduction
Increased Attack Speed
Life on Hit
Weapon
Thunderfury, Blessed Blade of the Windseeker Thunderfury, Blessed Blade of the Windseeker
Strength
Cooldown Reduction
Increased Attack Speed
Life per Hit
Socket (preferably from Ramaladni's Gift Ramaladni's Gift)
Off-hand
Freeze of Deflection Freeze of Deflection
Strength
Cooldown Reduction
Block Chance
Vitality
Follower Item
Enchanting Favor Enchanting Favor
Strength
Block Chance
Vitality
All Resistance