Maximizing resource gathering on the map is one of the key aspects of Dota. Being more efficient can lead to a snowball effect off the back of some small advantages and ultimately win you the game. One of such advantage is the “free” shard your team can get from Tormentor. Taking it is usually a team effort, however there are several heroes who can (and should) do it by themselves.
The trick with Templar Assassin is pretty simple. You want to stack double Meld and time your attack in a way that allows you to get the second Refraction as soon as the first one is exhausted.
Desolator is a great help when it comes to soloing Tormentor as all barrier damage is calculated post-physical damage manipulation.
The idea is to minimize the amount of hits you need to make and the general approach is use Refraction while running towards your goal. Get close to Tormentor and use Meld. Still sitting in Meld wait until it cools down and then go for two back-to-back Meld hits for massive burst damage.
You probably won’t get the second Tormentor with this approach, as it gets harder to do it in 12 hits or less, but the first, most important one, can even be stolen from the enemy in a pretty quick and safe way.
Ursa’s approach is even easier. Use Overpower on your way to Tormentor, wait until you have the second one at the ready and then go for it, using Enrage as necessary.
You usually want to use it when Tormentor is around 60% HP. Ideally, you want to time it so that it expires just as Tormentor dies. Using it too early means you are mitigating less damage, as Fury Swipes aren’t stacked yet. Using it late means you are probably very low HP at the end of it.
As such, Ursa is at his best when taking your own Roshan, as healing up is that much easier. Taking the enemy one is too risky without winning a fight or splitting the enemy across the map with the help of your teammates, so keep it in mind.
Troll’s DPS gains from Fervor are comparable to what Ursa gets from Fury Swipes. There is a hard limit on it, but when it comes to the first Tormentor, this limit is unlikely to come into play. So the idea is the same, perhaps even simpler.
Melee form with lower BAT is definitely a must, so is good ultimate timing. Outside of it, there isn’t really much to it. Troll really isn’t the trickiest of heroes.
A level 12 Slardar should have no problems getting the first Tormentor solo. This is possible because Slardar has access to one of the strongest Armor-reducing abilities in the game. Just make sure that you have enough attack speed.
Also use your Slithereen Crush before starting the work on Tormentor. Having a +Armor puddle when dealing with damage reflection is a must and will save you a lot of HP. There is a reason why Slardar’s default build nowadays is 4-1-4-1 by level nine: do not underestimate the power of small buffs.
Juggernaut isn’t the fastest Tormentor taker, but possibly one of the most reliable ones, courtesy of Healing Ward. This ability should be maxed out second in most games and a level 12 Juggernaut with appropriate farm should be able to solo tormentor.
Power Treads, 
Battle Fury and a 
Yasha derivative should typically be enough. Having a 
Wraith Band also won’t hurt and it is one of the better laning items in most situations.
That said, despite having an option of solo-killing Tormentor, Juggernaut is far from being a good hero in the current patch. Ever since his level twenty talent was fixed, it is really hard to recommend him for pubs, so perhaps it is better to pick one of the other options mentioned today.
There are probably other heroes who can solo Tormentor, without too many conditions and a lot of time spent on setups. Of course there is a level 12 
Techies, who can blow the Tormentor up with seven mines at minute 20, but it is not a reliable scenario.
If you have other ideas or tricks to share, feel free to do so in the comment section below. There are probably more heroes who can solo Tormentor with ease, increasing the efficiency of your team.