I'm sorry to burst your bubble but Bioware have also said that accuracy is useful for tanks, which is clearly untrue. Don't take what Bioware says to be the complete truth. I can guarantee you that 16 man is harder.
Also as another point: On 8 man the 2 tanks have 1 million hp each, 2 million in total (taking these numbers from videos) . Lets say dps have around 280 (numbers from 16 man, could be wrong) seconds of dps on the tanks, that means each of the dps needs to do around 1400-1500 dps (assuming 2 tanks= 1 dps). Lets compare this to 16 man: each tank has 2.5 million hp each, adding up to 5 million. Again, saying dps have 280 seconds to kill the tanks this leaves you with each dps needing to do aroung 1600+ dps (assuming 2 tanks = 1 dps). Correct me if im wrong but there is a clear dps requirement difference here. So to everyone saying 8 man is more of a dps check, please, prove me wrong.
You forgot the key mechanic of this fight on NIM, the second double destruction. If you getting the second double destruction (and you will on 8 man, unless you have uneven dps on the tanks) you will need to have people switch tanks mid fight, much like the tanks do, and loose out on dps from having to switch. On 16 man you can assign 2 dps to take the 1st DD, and then 2 others to take the second with out needing anyone to stop their flow of dps at all.