On 3.8.4-13 :
Random Writes : 470731.12 kB/sec
Disabling self heal showed no improvement on random writes(466813.44 kB/sec).nor did disabling io-threads as I mentioned in the description.
The number of INODELK calls have been increases considerably from 8 to almost 3000+ in 3.2,this may account for this regression.
Ashish can you take a look too?