Dirang Dzong fort is just a okay fort. or I can say, its not even a fort. its a just an old structure. which is not well maintained.
There was a old jail there. You can reach there by climbing some stone stairs.
The whole structure is based on budhist architecture. And now around the fort. there are buddhist local people living there. The structure is now rusting.
There are dried yak meats hanging on the strings there. soya beans are dried on the grounds. because of the local people
The best thing which I got from this place is watching the beauty of mountains and the waterfall on the opposite mountains.
Verdict- Go if you are passing from that area. or if you want to see the buddhist architecture. otherwise. avoid these place. you will not get much from this place.