Originally Posted by Kiido
Picking out DoT skills as the defining factor of a tank is fallacious. DPS is simply another form of damage, dealt over time. Hell, even arc lightning is damage over time (2.25 second intervals, rather than the usual one second intervals).
There is conceptually no difference between a radiance burn, a heartstopper aura, and a Mortred's physical attacks.
They are all damage-dealing skills, they are all time-sensitive, and they all deal damage directly proportional to how long the hero is on the field, making a hero that possesses any of the above a prime target, regardless.
With that in mind, the only factor that separates one form of threat-over-time from another is the overall battlefield impact. Sure, the radiance burn affects everyone, catching their collective attention. But if the enemy were to look at it rationally (not always the case, though), what do you think is more dangerous to them?
A radiance, dealing a total of 150 damage every second, split over 5 heroes?
Or a Mortred that's dealing 1k crits, attacking thrice every second, and who has the potential to completely remove one of your teammates in slightly over a second, as opposed to a measly burn of 30 HP/sec from radi?
Granted, psychology plays a role. The radiance burn is visually blatant. The Tidehunter that blinks into your midst is an immediate threat, which brings on your emotional responses, calling for immediate action. But against calm, experienced enemies, this attention-whoring tank strategy loses it's effectiveness.
DoT does not explicitly refer to actual 'DoT' skills like Poison nova, but more than a hero can consistently deal damage, over a long period of time, preferably without even attacking and dealing it in an aoe.
Its basically saying that heroes like centaur, who's damage is limited to Stomp+double edge combo, is fairly weak tank as opponents wont attack it as it poses no threat over a long period of time.
On the other hand, a necrolyte or dusa may not have an immediate effect, but if not dealt with quickly you will sustain a lot of damage, and their team mates will be much harder to kill.
On a hero like mortred, you dont want to tank, and you really wont tank, although its likely you will get focus fired when you dont have Bkb active.
Mortred excels when the oppponents are attacking one of your other heroes, and she blinks in and quickly destroys a support hero using her blinkstrike. Mort works best when she is unnoticed, hence the idea of 'phantom assasin'. Playing her as an actual 'tank' (vang+blur gives alot of survival) works decently, although she becomes minimalish threat and will be relagated to more of a ganker using dagger. If you dont agree, watch the showmatch with ZSMJ playing tank PA, and see how useless he was lategame.
Many heroes are high threats, its just the problem of whether they can remain high threats while only buying tank items, or whether they have enough mana and low enough cooldown skills to warrant them surviving longer and finally whether they need to be in the middle of the fight, as that will result in them taking many aoe nukes.
On a hero like lich, theres minimal point in tanking him up, since he probably already FA'ed his team, and if he gets off chainfrost, his Job is done and his only use will be frost novaing every 6 seconds. While a hero like zeus, who continuosly nukes would be a prime target, doing significant damage over a long time, but he is limited to mana, and in general tanking him up isn't as good as just positioning yourself correctly.
Finally: If a hero tanks damage, its highly likely that they will also get stunned. Hence, they often wont be able to actually attack and thus since tanks dont get bkb, its generally better if you can deal damage without attacking, E.g Alch with radi+acid spray.