As for Muhammad ibn ‘Abdul Wahhab al-Najdi, then indeed he was an idiotic man of little knowledge, thus he would be hasty in making takfir. Diving into this river (of takfir) is not appropriate except for the one who is cautious upon, proficient in, and well-acquainted with the existence of disbelief and it’s causes. 
ويقول ايضا في كتابه ( فيض الباري ، 1/171 ) : ( أما محمد بن عبدالوهاب النجدي فإنه كان رجلاً بليداً قليل العلم ، فكان يتسارع إلى الحكم بالكفر ، ولا ينبغي أن يقتحم في هذا الوادي إلا من يكون متيقظاً متقناً عارفاً بوجوه الكفر وأسبابه ).
The above quotes can be found in the Maktaba Rashidiyya edition under the following references:
which was signed by over
Ibn Abd Al Wahab al Najdi as mentioned in Durrul Mukhtar.
Now official fatwa from Deoband has accepted the aqida and approach of Ibn Abdal Wahab Njdi as correct. Here Deobandis are going against their own book, Al Muhannad.
This proves that Al Muhannad was written by Deobandis only to get it signed by Sunni Aarb scholars.
Al-Muhannad, the book of beliefs of the ulama of Deoband, on page 12, contains the following question and answer:
"Question number 12: Muhammad Ibne Abdul Wahaab held the view that shedding the blood of Musalmaans and taking away their property and defiling their honour, all these things were lawful. He also termed them idolaters. He was insolent towards the elders. What is your view of him? And do you (think calling the Ahle Qiblah as infidels is a lawful act? Or do you think that he who does these things belongs to a legitimate sect?
Answer: In our view (Please note: OUR VIEW (not My view) and Al Muhanned was signed by leading scholars of deoband school of thought) the same verdict applies to them as has been given by the writer of Durr-e-Mukhtaar. And Khawarij are a band of people who waged war against the Imam because they thought him to be guilty of falsehood, that is, idolatry, which justified waging war. For this reason they take the taking of our lives and our property and making our women captives to be lawful. He further held that they were rebels. He also held that they did not Describe them as infidels because this was a matter of interpretation, though a faulty one. And Allamah Shaami, in his marginal notes on the book, has said, "Like it happened in our times when the followers of Ibne Abdul Wahaab sallying forth from Najd overwhelmed Haramain Shareefain. They described themselves as belonging to Hambali creed, but it was their belief that only they were Musalmaans and whoever was against their belief was an idolater and, so, they justified the killing of the Ahle Sunnat and the ulama of the Ahle Sunnat until Almighty Allah deprived them of their ascendancy."
Hussein Ahmad Sahib Tandvi Madni says: "Gentlemen' Muhammad Ibne Abdul Wahaab appeared in the Najd in the 13th century A.H., and, because he harboured evil thoughts and held wrong beliefs, he waged war on the Ahl-e-Sunnat Wall Jama'at, sought to force his evil thoughts upon them and considered lawful seizing of their properties as the spoils of war, and killing them, and considered all these acts to bring blessings. He was harsh on the people of the Haramain (Makkah and Madinah) in particular and on the people of the Hijaaz in general. He used most foul language against the pious men of the earlier generations. Because of the atrocities committed by him on them, countless people had to flee the holy cities of Makkah and Madinah, and many of them were martyred by his troops. In short, he was a tyrant, a rebel and an altogether evil person."
(Ash-Shahaubus Saaqib, Page 42)
"Muhammad Ibne Abdul Wahaab believed that people all over the world and all Muslims were polytheists and infidels. (Page 44)
The Najdis believed, and his followers still believe, that the lives of Prophets (Alihumus Salaam) were limited to the times during which they lived upon this earth. Thereafter, in death, they and other faithfuls are equal. (Page 45)
This group holds that having a vision of the blessed Prophet (Sallal Laahu Alaihi Wasallam) and visits to his blessed tomb are bad innovations and unlawful. He also holds as unlawful even journeying in that direction for this purpose. According to some of them, even journeying for the sake of paying a visit to the blessed tomb is like committing fornication. May Allah save us from such evil thoughts! (Page 45)
The Wahaabis use most insolent language in respect of Prophethood and the person of the holy Prophet himself (Sallal Laahu Alaihi Wasallam) and, in their insolence, claim to be the equals of the personality of the holy Prophet, and, according to them, only a little benefit accrued from him during the times he was preaching the Messages of Allah, and no benefits flowed from him after his passing away. And because they think so, they consider as unlawful praying for Allah's forgiveness through his intercession. Their elders also said that praying for Allah's forgiveness through his intercession was unlawful. (May Allah save us from having such thoughts)! But, perhaps, it may be permissible to reproduce such thoughts, for merely reproducing blaspheming words does not by itself constitute blasphemy). They also said that the staff in a man's hand was of greater advantage to him than the glorious personality of the king of the universe (Sallal Laahu Alaihi Wasallam), for with a staff in his hand one can defend himself from a dog while the personality of the pride of the universe (Sallal Laahu Alaihi Wasallam) cannot do even this much for him. (Page 47)
The Wahaabis are against performing mystic rites and sophistic practices-meditating, engaging in the remembrance of Allah and thinking about Him, owing allegiance to spiritual guides and the whole system of spiritual guides, and having a mental rapport with the spiritual guides, believing in the doctrine of annihilation and permanent life etc. etc In their view, al' such things are of no consequence, bad innovations and demeaning.
(Page 59, Ash-Shahaubus Saaqib)
In Wahaabi belief, following any particular Imam is considered to be blasphemy against the Prophet, and they use wretched and wicked words for the four Imams and their followers, and thus they are alienated from the Ahl-e-Sunnat-Wa-Jama'at and so the non-emulators of India belong to this wicked group. While they claimed to be Hanbalee when they first appeared on the scene, but in many matters they do not follow Imam Ahmad Bin Hanbal (Alaihir Rahmah) (Page 62, Ash-Shahaabus Saaqib).
Through verses Ar-Rahmaanu 'Alal 'Arshis Tawa etc, the Wahaabis try to prove that Allah physically occupies a throne and also make out His dimensions and, therefore, His bodily presence.
The Wahaabis of Arabia have often been heard to harshly denounce the expression, "As Salaatu was Salaamu Alaika ya Rasoolal Laah" (Peace and salutation to you, O Allah's Messenger)", and most scathingly condemn and ridicule its use, and hurl most unbecoming language against the people of the Haramain who use such an expression.(Page 65, Ash-Shahaabus-Saaqib)
The wicked Wahaabis harshly denounce sending repeatedly peace and salutation on the mercy to the worlds, and consider reciting Dalaa'ilul Khairuat, Qaseedah Burdah and Qassedah Hamziyah and such like as most detestable and unwarranted. They also consider some couplets of Qaseedah Burdah to be downright blasphemous, as for example the couplet:
Ya Ashrafal Khalqi Maali Man Aloozu Bihi Siwaaka Inda Huloolil Haadisil 'Amami
(O. the best of creations! I have no one To look up to in perilous times like these)
(Page 66, Ash Shahaabus Saaqib)
Except for the knowledge by him of Allah's commands, the Wahaabis think the personality of the Last of the Prophets (Alaihis Salaatu Was Salaam) to be devoid of all hidden and true knowledge.
The Wahaabis consider the narration of the birth of the king of the universe (Alaihis-Salaatu-Was-Salaam) itself to be a most reprehensible act and a very bad innovation".
(Page 67, Ash-Shahaabus Saaqib)