Similar channels have created a review video on Heroes of the Storm including main channels and informative companies such as IGN and GameSpot, however, these tend to include all gameplay footage with an audio overlay reviewing the title as opposed to the footage being shot live. Although these are informative they lack the comical aspect that many YouTubers dedicated to this field have.
Other reviewers such as AngryJoe do incorporate a mixture of real-life footage alongside their in-game content however, these tend to be more of a comical factor as opposed to being purely factual and serious.
There are also little to no reviews on Heroes of the Storm past the alpha/beta stage of the development of the title therefore creating a year one review would appeal to many people and perhaps generate an interest in a MOBA that is currently overshadowed by the larger titles in the genre such as League of Legends, Dota and Smite to name a few.
Although it has to be noted that IGN does specialize in other areas than gaming reviews hence the 7 million approx. subscribers in YouTube with having their own website and other forms of media. In comparison, AngryJoeShow has 2.5 million approx subscribers on YouTube and mainly features content such as gaming reviews as well as reviews on other types of media such as films and tv shows. This may not prove that only gameplay only based review content does well but rather the size of the company to begin with as having 2 million subscribers is still a high number in consideration.
Both companies monetize through the use of advertising such as IGN