I think I would dump a fair bit more money into advertising, then go full "Genesis does what Nintendon't" in terms of advertising.
What I mean by that is that every gamer and their mother knows what League of Legends is, and most of them know DOTA 2 as well. We know how much of the market share they have cornered. So, I would play with that a bit. I would run commercials mocking the MOBA genre as a whole. They would start with a gamer mindlessly staring at his computer, clicking away in lane in some fake MMO that's been designed to look slow and boring, with the players' characters just dancing around one another clicking on minions as the commercial goes into timelapse, cutting to ten minutes later where the gamer is STILL doing the same thing, and has noticeably grown even more bored than they were previously. Then, in the background, their TV flicks on.
"NO MORE MINDLESS LAST-CLICK FARMING FOR GOLD IN LANE! NO MORE CREEP DENYING! NO MORE MONOTONOUS SINGLE-MAP GAMEPLAY! NO MORE PAGES OF ITEM LISTS TO MEMORIZE! NO MORE BOREDOM! SIGN UP FOR HEROES OF THE STORM TODAY AND DIVE RIGHT INTO THE ACTION FROM THE VERY FIRST SECONDS OF GAMEPLAY! FIGHT WITH YOUR FRIENDS IN GLORIOUS BATTLES IN THE MOST BRAWL-ORIENTED ENTRY IN THE MOBA GENRE YET!"
Cut to that gamer, clearly feeling curious, signing up for an account and promptly logging in, only for the computer screen to open up like the arc of the covenant, brimming with light as the gamer's hair is literally blown back.
Cut to big, bold quotes from reviews like the updated 2018 IGN write-up that emphasize how fast-paced and fun the game is compared to other MOBAs on the market, speeding through praise after praise to make a very clear point to any naysayers watching the commercial.
Finally, cut to a montage of high-octane gameplay. Clips of things like Falstad gusting an entire team of enemies into his own allies, or wombo combos with abilities like Gazlowe's Grav-o-Bomb. Show off a boss pit and a cataclysmic wipe, then zoom in on the mid-match clock to show that something so exciting happened only ten minutes into a Heroes game. Show off some skillful gameplay too, like an amazing Alarak or Kerrigan play, just to show potential players just how high the skill cap truly is, even if Heroes has a public stigma of being an "easy" MOBA. Rush through clip after clip like this in rapid succession for a number of seconds before signing off with info about where people can sign up for an account.
This is just a small thing I would do, granted, but I think it's the most important thing for the longevity of the game. Some players want to leave other MOBAs, but they don't know what the other features of other games in the genre are. So, show them the difference, and how fast-paced Heroes is compared to slower gold-farming MOBAs.