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Video length is ok. Most people won't watch far past 10mins unless they're particularly loyal or interested to find out what happens in the end, so PvP battles are ideal for longer videos as they have that "who will win?" factor. My audience is currently stuck around the 3-4min average view time for example so I've started cutting my videos shorter if they're simple Guilds or Information videos.
Following on from that - "How to" and similar guide videos do well in my experience, be clear with your instructions and keep things simple.
I've found diversifying difficult with poor audience take up on videos outside of the core pocket of subscribers ..for example most videos what aren't Tom Clancy related!
I see you're on console so I'm not sure what editing facilities are available to add an animated or even a static intro for example. I need to invest in a proper one myself (i.e. paid for) at some point as I'm using a free version.
Advertising and self promotion on external forums, official forums, social media is very important as well.
...you'll likely get a ton of spam messages & comments on your channel once you get to a certain point. I know I do.