The difficulty of Ninja Exams actually gets lowered depending on how many players in your merged servers have completed it before you. You can check by clicking on "Ninja Exam Heros" and there click on "Details". Also there is a certain time that needs to pass after those players cleared the exams in order for the difficulty lowering to take place. Below is a picture for reference:

Edit: What I meant to say is that it's possible that those people you watched in the video had the difficulty decreased much more than in your server and therefore being able to kill units faster/take less damage.

Thank.

This all, complexity will not decrease?

Hmm not to my knowledge. The only other explanation I could think of is that the people you saw in the video had much their power much more focused around their p1 ninja. You said that the people in the video "killed faster" which could also mean that their p1 ninja that was doing most of the damage and had much better equipment than the rest of the units in their lineup. This used to be very common (and it still is) but today we get most of our power through Training Potions or Secret Scrolls which distributes the power evenly between each position while back then it was all about Charms, Refines, Rune Stones and Magatamas resulting in the p1 ninja having much more power than the rest of the units in your team. So in a way it also depends on what date that video was recorded.

Understan, i will suffer, thank.

P.S. China 1 year ago.

you wrong check, you check in level 125 in picture but you say about ninja exam lv 410 you must drag that scroll

Yes, yes, sorry, need wait 1 month. This 2 point 1 month and 45 day.

How long wait, who know? Yesterday too 31 day.

Nobody know, just check it every day till it sais completed.

Ok, thank.

on the CN servers the ninja exams has been upgraded till level 500 and soon it will be 550.