Tahirih and all of the other Letters of the Living have just as much authority as the Bab. The Bab saw it this way, the early Babis treated them with the same authority and reverence. You see this even in the writings of Baha'u'llah from before his declaration. At the end of his
Sahifiy-i-Shattiyyih, he offers a
shahadah of sorts to the Bab, Quddus, and the rest of the Letters of the Living:
This is just a grave misunderstanding of the Revelations of both the Bab and Baha'u'llah.
It is correct that a lot of us can not read Arabic and Persian and thus can not say much about untranslated writings. The great thing here is Baha'u'llah gave a covernant to which the successor, who was first Abdul'baha and then Shoghi Effendi, were able to make clear as to what was revealed in the Writings.
They did a great job and obviously foresaw the turmoil in the future. They both explained the most important aspects of these twin Revelations and made sure translations were available of writings that would cover all these difficult areas of meaning.
The stations given to the Letters if the Living were symbolic, this is a reference to Quddus;
"Regarding the station of Quddus, he should by no means be considered having had the station of a Prophet. His station was no doubt a very exalted one, and far above that of any of the Letters of the Living, including the first Letter, Mulla Husayn. Quddus reflected more than any of the disciples of the Bab the light of His teaching." (11 November 1936, written on behalf of Shoghi Effendi to an individual believer).
We also have the Universal House of Justice, also under the Covernant of Baha'u'llah who have also clarified this matter;
"It may be helpful to consider that in the Dispensation of the Bab, Quddus is referred to as the "Last Point", and the "Last Name of God", is identified, as pointed out in God Passes By, with one of the "Messengers charged with imposture" mentioned in the Qur'an, and is one of the "two witnesses" into whom "the spirit of life from God" must enter, as attested by 'Abdu'l-Baha in Some Answered Questions, yet, despite these sublime stations, he is not regarded as an independent Manifestation of God." (24 August 1975, written on behalf of the Universal House of Justice to an individual believer)
There is a truckload of advice available on this topic.
Regards Tony