Question:

Turkey to India, overland via Iran and Pakistan - is it do-able? Some websites advise against a) crossing the border from Turkey into Iran; and b) from Iran into Pakistan on account of the lawlessness, corruption and risk of terrorist related activity.

Answer:

There are only two borders opened to foreigners between Iran and Turkey. The first is the Gürbulak–Bazargan border near Dogubayazit (Turkey) and Sahabat (Iran) - it is the busiest. The second border crossing between Van and Khoy is called Esendere–Sero and it is further south. The road turns into a dirt road up in the mountain.
It is better to make sure it is open if you're planning to cross during the winter. The road thourgh Dogubayazit is a beautiful region with the stunning view of the Mount Ararat. The road going through Esendere-Sero is even more scenic.
You can find Sero border on Google map at 37°43'24"N 44°38'26"E.

Mirjaveh is a locality in eastern Iran on the border with Pakistan. It is the main road crossing point between Iran and Pakistan. The Pakistani border post is at Taftan. Mirjaveh is also the point where the railway line from Pakistan crosses the border on the way from Quetta to Zahedan.
The border immigration opens in the Pakistan side around 9am. There is a gate only on the Iranian side.

Check the cheapest Iran tours.