>>1852250/300/350 dmg to the entire opposing team is it not? Plus the bonus attack damage for all your illusions. Its not going teamwipe in itself, but it can pop escaping bad guys or make the enemy hesitate in their engagement, fracturing their team.
>>1845the shield doesn't counter your passive, think of it like this. You only have so much health you can lose before die, which means only a set amount of damage can be inflicted with the passive before you die. The shield stops you taking damage, but they'll still have to inflict that damage on you to kill you, so they'll still take that damage eventually. It slows everything down, which as a tank, is exactly what you want.
> any form of silence or even a mere stun while my ult is on cooldown would turn me into some carry's mealThats what your escape, your passives and your team are for. You are the hard carry, you should have total farm priority, when you can't get it you go elsewhere and your team should move in to deal with the problem you couldn't tackle solo. Obviously in pubs this may not happen as it should. An early BKB is a must, as is a Vanguard and probably a wand.
>so why not just get diffusal every game?Diffusal has its uses, if mana draining/purging is going to be particularly effective against the opposing team, Medusa for example, then I'd get it. Otherwise you'd be better off with a Manta for silence purging, spell dodging, more illusions and a plethora of other things.