GPU temperature around 83 - 85 degrees while playing overwatch on Medium (Alpha R2 w/ Geforce GTX 960)

GPU's do heat during game play so yes this is normal.

Idle can be 32c and go up to 89c under heavy loads. 80c to 98c is not uncommon.  98c tends to be max though because at higher temps failures can occur.   You are going from 19w idle to 119w full speed.

Also keep in mind that temperatures of the actual gpu vs sensors can vary as much as 15c from what it actually is.

Also keep in mind that temperatures of the actual gpu vs sensors can vary as much as 15c from what it actually is.

That's a good point.
 
People think that just because a thermometer is "solid state" it's exactly accurate, but this is simply not the case. I've also seen thermometers in extreme temps (either hot or cold) get worse over time.

Thanks for the answers guys - Good to hear that despite my uni sounding like an Apache trying to take off, the temperatures are not a concern (I'm testing it using Speccy & the in game GPU monitor, both recording the same temps).