All content in this game is easy. That being said if you look at 16m videos v 8m videos at least for the styrak fight 16m is even easier. the dmg ticks for the same in both modes from KD spikes only you have 2 less healers in 8m. The hp differential isnt much as 16m gains 6 more dpsers to compensate. The tanks take the same amount of dmg as well. Images in 16m do have 6k more hps than the 8m version. channeled manifestations in 8m have 211k hps and in 16m 390k so once again its an easier burn in 16m. The biggest difference however seems to be the enrage timer. In 8m you get an 8 minute enrage timer compared to an 11 minute enrage timer in 16m. Seems like if you want a slightly bigger challenge from this easy content you would have to run the 8m version.
Edit: Also I just worked out the math with the enrage and hps and amount of phases being equal in 8m and 16m. In 16m the dpsers only need to do 1530 dps each to beat the enrage timer while in 8m the 4 dpsers need to pull 2450 dps each to beat the shorter enrage. I'm sure those values would change a bit if you add in the tank and healers doing dmg as well but thats the pure dps dmg requirement needed.
Having cleared both 8 & 16 I can confirm all of this. It's frustrating but my group has switched to 8 after we cleared 16 the first week.
enrage on styrak on 16 is at least 11+ mins on 8 it is 8 or so mins.
You are off on the 2400+ dps but I'd say 2200+ for sure.
Hopefully for NM they up the fights like it was in older content where 16 on most fights was more difficult. If they don't outside of the achievement I'll refuse to do it.