There are important plot details you've got to see at the beginning and end of Avatar 2. If you've got the time and desire watch the 2nd one first.
It's just that Cameron could have condensed much of the story from 2 and 3 into one movie over all. I bet some fan will edit them together into a super cut after 3 is released to home/digital.
To me it was like he said, I can introduce this new tribe and.....then immediately evert back to the plot of part 2. When they got captured, instead of escaping right away they could have scenes with them all held captive by Vangra and then Bedwench comes in to help save them.
Cameron was so quick to revert back to what he already did in the previous flick and that was kinda disappointing.