Audio does need some work it's very hard to understand what you are saying as well as the sound levels. You may want to try bumping that up a bit
While you are at lower subs I'd also suggest keeping videos shorter, around 10-15 minutes for lets plays. A 20-30 minute video can be very daunting for new viewers and you don't want to turn away views just because of that. Everything else looks pretty good though, keep on at it and I'm sure you will grow.