There's definitely more things you can try. With a number of your videos I think a main issue is people being able to find those videos. A lot of the lets play videos don't really have anything in the title that people could search for other than the name of the game which would be likely very competitive. I do a lot of lets play style videos but I never title them lets plays I always go after more specific keywords. I started my Castle Crush series with 10 lets play videos that did okay, but I started getting the real views after I switched to more specific video titles and themed challenges.
So just looking at your most recent video, opening loot boxes is in theory a great video idea and something people would search for. However Overwatch is so competitive content wise that unless you were very prompt about making the video after they release you might still have trouble getting seen. Making those videos as soon as possible after the boxes release is what I would try to do. With the text in the thumbnail the key words that might make people click are Summer Loot Box and you have those which is good, but the word "Loot" is covered up slightly so I would try to avoid that. People are more likely to click because they see the word loot than the characters you have next to it.
Looking at the video tags for the loot box opening, I would avoid using one word tags like "summer", or "pack" or "event", because you search the word "event" and you are competing against 59 million results and most of the people searching that are not looking for Overwatch. If I search "overwatch summer loot boxes 2017" you only have 170,000 results to compete with although it's still fairly competitive. However, look at the search results. Nobody on my first page of results used that exact keyword in their title. I would find multi word keywords that you think people are searching for and base your video titles around those. If you use the exact keyword in your video title and nobody else does then that's an advantage to you for getting videos ranked.
In order to rank for these longer keywords, most of what you have to do is just make sure it's in the title, description, and video tags. And make sure what's in the video relates to it.
If I were going to craft a video around opening the loot boxes just as a challenge here, I might title it "Opening 12 Overwatch Summer Loot Boxes 2017" or just "Opening Overwatch Summer Loot Boxes 2017" because 12 doesn't sound like that many, and then include "overwatch summer loot boxes 2017" as a video tag and also put the exact keyword in description(use it in the context of an actual sentence).
I can't say any of that would help after the video has already been posted but for future videos I would consider trying to work keywords that will be easier to rank on or doing video topics that may have less competition like tips/guides/weapon or new hero reviews rather than gameplay. Overwatch is tough but other games with less competition might be easier. BTW I know you play other games than Overwatch but it was a good example.
Thanks!
