I sure think so. Its base protection is 1, with 50% fire/acid/plasma resistances. If you assemble nanofiber skin energy-shielded vest, you're up to 25% melee/bullet/shrapnel, 75% fire/plasma/acid, and the armor becomes indestructible and self-regenerating. Add on a power mod pack and you have 3 protection, 25% melee/bullet/shrapnel, 75% fire/plasma/acid. At this point, all non-boss enemies that deal fire, acid, or plasma damage are either guaranteed to deal 1 damage or have a small chance to do more than one damage. Archviles always deal 2 damage, Mancubi and Revenants have a tiny chance to deal 2-3 damage, Nightmare imps have a 1/36 chance to deal 2 damage, Nightmare cacodemons can deal up to 3 damage, Nightmare archviles deal 3 damage, the shambler deals up to 4, etc.
And it gets better. With three levels in tough as nails, the only ways you can get hit by more than one damage are:
Attack (Max Damage)
Seargent shotgun at distance of 1 (4)
Seargent shotgun at distance of 2 (2)
Baron of hell's melee attack (2)
Mancubus' melee attack (2)
Nightmare demon' melee attack (4)
Nightmare cacodemon's melee attack (2)
Nightmare archvile's melee attack (2)
Shambler's ranged attack (2)
Shambler's melee attack (2)
Bruiser brother's melee attack (2)
Lava elemental's melee attack (2)
Cyberdemon's melee attack (8)
Cyberdemon's ranged attack (3)
Angel of death's melee attack (8)
John Carmack's melee attack (8)
John Carmack's ranged attack (3)
enemies that fire multiple times per turn
As you can see from the list above, the chances of an attack dealing > 1 damage are small. Most of the possibilities for taking > 1 damage involve melee attacks from enemies which prefer to attack you with ranged attacks (and deal less damage with ranged attacks). Most of the max damages listed in that table will never be inflicted upon you; for instance, the chance that JC's/the Cyberdemon's rocket launcher will deal 2 damage to you is less than 1 in 50; the chance of 3 damage is 1 in 1666. Probably, the only attacks that deal > 1 damage that will ever actually be inflicted upon you are the Angel of death's or the nightmare demon's melee attack (but the angel of death does not spawn randomly, even in Ao100, and chances are you'll have a hatred skull ready when you face the angel of death in the unholy cathedral).
Furthermore, if you get entrenchment (which does not block tough as nails), then you are truly invincible.
Now, I do acknowledge that enemies that fire multiple times per turn can deal more than one damage per turn. Still, what they deal is almost negligible when the hard hitters like nightmare archviles and revenants are guaranteed to deal 1 damage to you per attack.
To attain near-invincibility, all you need is:
2-3 power mods and a nano mod
an energy-shielded vest
1-2 levels of whizkid (you could get by with only one, but an extra level in whizkid allows you to add another power mod and get extra protection = two levels of tough as nails)
(optional) three levels in tough as nails
(optional) entrenchment
Are the mods and the vest guaranteed? Of course not. But in my experience the vest is not rare, and you have a decent chance of getting a nano mod especially if you visit the armory. If you're playing Ao100, the odds are even better. And when you do get the right ingredients, the combination is just overwhelmingly powerful. Every other armor, unique or assembled, is far less powerful, even those that are far more difficult to obtain. Even cybernano cybernetic armor (P1) is not as powerful, especially against plasma attacks.
All of my numerical information was obtained from the wiki. My calculations were done under the assumption that .5 rounds to even.
