Sri Rudram occurs in all 101 Shakhas of YajurVeda and hence called SataRudriya also (which I discuss here.) 8th Anuvaka of Sri Rudram (of Taittariya Samhita) is of special importance because of revelation of Panchakshari Mantra ie. "Namaha Shivaya" in this AnuVaka.
Shiva denotes the transcendental aspect which is beyond 3 Gunas (ie. Turiya state) (which I discuss here.) It is basically Saluting the transcendental state of Lord who is beyond the Tri Gunas.
Panchakshari Mantra is of special importance. The five letters "Na" , "Ma" , "Shi", "Va" , "Ya" denote the five heads of SadaShiva as I discuss here. Vedas also enter inside Panchakshari during the Pralaya Kala which I discuss here. Similarly, another importance is one can also change his Varna through the application of Panchakshari Mantra which I discuss here.
FurtherMore 8th Anuvaka is also of specific significance due to revelation of other things which are concerned with worldy state and liberated state:
➡➡ Parameswara along with Uma removes misery of Samsara:
8th Anuvaka starts with "Namaha Somãya Cha Rudrãya Cha." ie. "Salutations to him who is with Uma and who removes the cry of Samsara (Rudra). It is of significant importance because whenever we see in scriptures that Lord Shiva goes to give boon to any devotee we see phrase like "Saha Devya Maheswara" "ie. Maheswara along with Uma (Devi). So, the form of Parameswara who is with Uma removes the misery of Samsara. Same thing is shown in Kena Upanishad. Also in Kaivalya Upanishad which states:
"उमासहायं परमेश्वरं प्रभुं त्रिलोचनं नीलकण्ठं प्रशान्तम् ।
Meditating on the Parameswara, allied to Uma, powerful, three-eyed, blue-necked, and tranquil..."
➡➡Parameswara is in the form of Sun:
Although the 1st Anuvaka of Sri Rudram clearly states it is Parameswara himself who is in the form of Sun. But the occurence of "Nama Tãmrãya Cha Arunãya Cha" readvocates that not only Sun but the Colour seen in the Sun is also Parameswara himself.
➡➡Parameswara as Pashupati provides comfort to all:
By the statement "Nama Shangãya cha Pashupataye Cha" (Salutations to him who provides comfort and salutations to Pashupati) it is seen that Pashupati form of Parameswara provides Comfort to all (by removing the Pãshas).
➡➡Parameswara is in fierce manifestation and fear in Gods:
By the statements like "Nama Ugraya Cha Bheemãya Cha" it is seen that it is Parameswara who is embodied in fierce manifestation of creation (Ugra) also the fear of him causes the Gods to respectively perform that function (Bheemaya). Katha Upanishad states
2.III-3. For fear of Him, fire burns; For fear of Him, shines the sun; For fear of Him, Indra and Vayu function; For fear of Him, death, the fifth, stalks on the earth."
➡➡Parameswara kills before one kills in the battle:
By the statement "Namo Agrevadhãyacha Durevadhãya cha" it is seen that it is Parameswara who kills first in the battle then only he is killed (Agrevadhãya). ie. The real killer in battle is just only namesake. It is Parameswara who does that task. Similarly it is Parameswara who kills in distant also (Durevadhya Cha). Same thing is seen in the Mahabharata where both Krishna and Vyasa tell to Arjuna that "the person who was killing remaining in front of Arjuna was Rudra."
➡➡Parameswara Punishes the evil doers:
By the statement "Namo Hantre Cha Haniyese Cha" it is understood that it is Parameswara who gives little trouble and very high trouble (as per the Karma of evil doers). Also the term "Haniyeshe Cha" indicates that it is Parameswara who destroys everything in the end. ie. Who is PralayaKarta.
➡➡ Parameswara is in the form of Pranava:
By the statement "Nama Tãrãya cha" it is understood that it is Parameswara who is in the form of Pranava / Omkara / Taraka Brahman. Parameswara in the form of Taraka as Omkara provides Moksha. The Atharvasiras says:
अथ कस्मादुच्यत ओङ्कारो यस्मादुच्चार्यमाण एव
प्राणानूर्ध्वमुत्क्रामयति तस्मादुच्यते ओङ्कारः ।
Why he (Rudra) is called Omkara? Because he sends the souls upward, at the time of dissolution.
➡➡Parameswara is the cause of happiness, comfort and bliss in this world and in the liberated state:
By the statement "Nama Shambhave cha Mayobhave Cha" it is understood that Parameswara is the cause of happiness in this world (Shambhave) and cause of happiness in liberated state (Mayobhave ). By the statement "Namas Shankarya Cha Mayaskarya Cha" it is understood that Parameswara is the provider of comfort in this world (Shankaraya) and provider of comfort in higher worlds (Mayaskarãya). By the statement "Namaha Shivaya Cha Shivatarãya cha" it is understood that Parameswara himself is in Turiya state (beyond Triguna) and Parameswara is the provider of Turiya state (Shivatarãya)
➡➡Parameswara is praised by the liberated ones:
By the statement "Nama Pãryaya cha Vãryaya Cha" it is understood that Parameswara is praised by those who are beyond (Pãra) this samsara ie. In liberated state (Pãryãye) and also by those who have not yet crossed river of Samsara. Ie. Who are in this side also (Vãryaye)
➡➡Parameswara helps to cross and finally liberates:
By the statement "Nama Prataranãye cha Uttaranãye cha" it is understood that it is Parameswara who helps to cross river of sins (Pratarana) and it is Parameswara who finally liberates ie. Taraka (Uttarana)
➡➡Parameswara makes the souls enter and encourages:
By the statement "Namo Aataryãye cha Aãlyadhye cha" it is understood that it is Parameswara who makes the soul enter in the womb (Aataryãye) and who encourages jeeva to enjoy fruit of it's action (Aãlyadhye)
Above described are the salient features of 8th Anuvaka. It is of special importance because it is concerned with both worldly and liberated state. So, it is chanted with special priority. 8th Anuvaka reveals that Parameswara is the cause of liberation of Jeeva and also binding of Jeeva, Parameswara is provider of comfort and bliss and as well as punisher and tormentor.
Regarding benefits of chanting it, it is itself clear from the meaning of Anuvaka. The chanter gets grace of Parameswara along with Uma. The chanter gets comfort and bliss in this world and also finally gets liberation. That's why the Kaivalya Upanishad and Jabala Upanishad recommended chanting of Sri Rudram hymn for liberation.