It can't be used on champions until they finish clearing anyways, and plenty of junglers find it impossible to safely clear without going back to base after their first buff.
And by safely, I mean without dying to camps or the light breeze caused by a counter-jungler's breathing.
Deep Terror Nami2 votesplenty of junglers
I'm sure there are a few actual junglers that don't clear well, but I wouldn't describe it as "plenty" unless you're including a lot of champions that aren't really junglers. You can't do the same exactly build and clear path on every jungler and get the same results. Some do better different ways. The ones that have issues can just get help.
FantasySniper1 votes
Others that I haven't even played, but know for a fact that people find it difficult to get through their first clear without breaking into a nervous sweat. If by "better different ways" you mean getting a lesser leash from top lane or risking your first buff and blood by killing the Scuttler, you should know that only makes it worse when it comes to clear speed and safety.
The ones that have issues can just get help.
Are you seriously suggesting that an extended leash should be a requirement?
Mat7itan1 votesRek'sai's first clear is super easy.... she has pretty much no trouble with it.
LostFr0st1 votes -->start 
and you should never really have trouble clearing. He's also one of the few who's best start is soloing gromp (even w/o a leash).
If you really need health on any jungler go chase scudz for a bit; he'll get you back to at least half and you can keep clearing.
FantasySniper1 votesChasing Scuttler at low health makes you an easy kill. Even if you started with Krugs + Red and have a CC spell, it still takes so long to do it, you might as well back.
LostFr0st1 votesBacking isn't worth it that early; you don't have to finish Scuttler,
just hit it a bit for the top-off.
I've died maybe once doing scudz (wasn't paying attention) and I usually drop a ward for top/mid or bot before I chase it.
If you're watching the map there's absolutely no harm in it.
FantasySniper1 votesIt is if your champion can't handle a normal jungle route. The other Hunter's item will provide enough sustain that you don't need to really worry about your health. Just hitting Scuttler isn't worth it, either. A lot of the healing you're doing is health regeneration up until the moment you kill it. And if you have to run while taking it, you're going to either smite it or you just left it softened up for the enemy jungler while you leave with nothing. I've both won and lost duels at river. A good amount of the duels I've won were because I jumped on the guy while he was trying to take Scuttler. A good amount of the duels I've lost were because I was jumped while trying to take it. The routes into river have sharp corners and bushes, so it's not easy to predict if someone is coming, especially if you don't have any wards on you.
LostFr0st1 votesWait, you start 
on Kha?
Let's back up a bit; you meant as examples of bad or good clears?
I read it as bad clears so maybe I'm reading you wrong.
Hitting scuds is purely to proc 's unique passive's regen. It's why it's better than machete in many cases.
It has nothing to do with which champ you're playing; it'll regen a chunk for 
even (lowest regen in the game) as long as you have it on you.
FantasySniper1 votesI don't get Machete on Kha. If you're referring to leeching off of Scuttler, I was being general. Assuming you're letting the Talisman do its work, you're slowly acquiring health over a long period of time. In that same or an even shorter period of time, you could back to base and get health from the fountain while also coming to possess another Hunter's item to sustain and damage camps with.
LostFr0st1 votesTo each his own I guess. Personally I don't like basing that early so I smack scuds a bit. Thanks for the discussion though^^
Deep Terror Nami1 votesWhen I have trouble clearing, I only blame myself, not the champion. I watch the Challengers do it to learn what I'm doing wrong. Leashing is a requirement of a player that needs help, not a champion.
Shiroi Kitsune1 votesSeriously... "impossible to safely clear without going back... after their first buff". Is this some kind of joke? The number is very low, and those that are get extremely strong late as a consequence. 
for instance.
Cloud2731 votesMaybe some of these junglers with bad clear times are supposed to be weak early game. Maybe, just maybe...this is something Riot did intentionally.
Slack King1 votesYou sure you are running the right jungle runes bud? I usually go krug/gromp, buff, buff gank
FantasySniper1 votesI've tried everything except spellvamp quints. Lifesteal quints work, but they make clearing noticeably slower. The route I usually do is a leash then smite on Krugs/Gromp > buff > smite then clear Gromp/Krugs > buff. If I plan on ganking sooner, I do the route you said. I back after the first buff if the champion can't handle anymore.