Don't question it. I did at one point. Then I became enlightened after trying it.

NOTE: While I saw this originally in OGN from Kakao, since I can't get his rune page or masteries I improvised, and this is what I felt worked best.

tl;dr Cap CDR early. Spam spells. Destroy people with absurd base damages. Spam snares.

You don't need to worry about missing skillshots either, since you literally need to only hit a target with snare when you are right next to them and then resnare them for your team to kill them. You are also tank rengar so you cannot be bursted.

Step 1: Get 5 Ferocity

Step 2: Activate ult and jump on target.

Step 3: Land snare.

Step 4: Cycle through regular abilities.

Step 5: Resnare target since you will have 5 ferocity again.

Step 6: Wail on target until dead.

Step 7: Go back to jungle and farm until your ult is up again, which will be soon due to how much CDR you get early.

Learn how Rengar leap works out of stealth to make sure you never miss snares. You can snare while in midair.

Always get Battle Roar off on as many targets as possible. If you get a 5 man Battle Roar you are unkillable.

When getting chased make sure you spam Bola Strike backwards to build ferocity.

Battle Roar grants you resists even if you do not hit anyone, but if you hit nobody you do not get ferocity.

Savagery is no longer consumed on towers, but you can still use it as an auto attack reset, kind of like Renekton's Ruthless Predator.

Thrill of the Hunt alerts enemies to your presence slightly out of your jump range. Keep this in mind at all times when ulting.

Almost always start with the ward version of Bonetooth Necklace. Once you are about to start grouping sell it for the sweeper version. You retain your stacks.

Savagery deals 2 damage to wards.

Empowered Battle Roar heals you more when you are low hp.

When running you generally want to prioritize empowered Bola Strike over empowered Battle Roar. The exception to this is if you know you will be taking fatal damage if you don't heal immediately.

You can still jump 0.5 seconds after leaving brush.