I for one enjoy these sort of videos so let me give some different perspective
. The editing was excellent as they stated. I LOVE the full HD that is always nice to see. Now, you can get popular with these sort of videos (or at least relatively so) but you need to do several things imo. Before I start let me say almost all of these are things Heir of Carthage does and I love him so i am biased
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1. Be nice and respond to your viewers. Nothing makes you lose subscribers faster than a mean-spirited or condescending response. Look at POM I love him but many people prefer Heir of Carthage partially because of the attitude.
2. Speak clearly and don't just narrate what is happening. Give insight into the game and try and engage your audience. Additionally, talk about yourself, if you haven't posted in a while explain why. This sort of thing is actually quite interesting and a nice change of pace from a normal "lets play".
3. HAVE VARIETY. Doing just one campaign on one game can get boring. Switch it up use multiple games (preferably ones that still allow #4) and also do MP & SP.
4. HAVE FUN. Nothing is more boring to watch than someone doing something just because they have to. Play while you are enjoying yourself and its more likely the audience will enjoy it.
5. Do collaborations. Play against other big name Total War Youtubers. This will garner you new subscribers, more interest, and future plugs.
6. Action. Good cinematography goes a long way when dealing with youtube. It is very hard to sit through an entire 13 min video if there are no battles breaking it up. Adding a samuari slicing open a ashigaru, a massive explosion or a synchronized volley wont hurt either. I literally just watched an 52 min long "lets play" and I didnt even notice the time.
Ill subscribe and watch more videos just to see how things go
Good Luck