I am more commenting on the "type" of person they feature in these videos, which seem to be everywhere in gaming media yet nowhere out in the real world. These overly quirky and excited over nothing types.It's a lose-lose situation when doing trailers like this. Either devs do it and have to force a smile and try their hardest to be charismatic, or they hire a famous actor, YouTuber, or voice actor and it ends up appearing just as forced for different reasons.
They were much more successful when they would show up and just talk about the feature sets of their games. Sometimes people were awkward but that's natural so it was fine. They didn't need any fake hype or singing the name of the game while shaking their body type antics. Who is that singing appealing to? And why does it come across like they are addressing children? Surely they know that the traditional blizzard fan is nothing like this? I know Hearthstone picked up some casual players but those guys aren't watching your live stream.
To be fair though, you are right and it is a lose-lose. The fact that this is mobile I don't think it was possible for it to appeal to me no matter how they presented it.