I would like to suggest that Valve make a single player campaign for Dota.

Now before anyone claims that Dota is supposed to be a PvP game, let me remind you that there are tons of PvP games out there with a single player campaign. The intent of the suggestion is to slowly ease the players new to Dota to its immense depth while holding their interest with the immersion of single player campaign. Dota is not anymore limited by being a mod in WC3 and being worked on by voluntary developers. Dota is now a standalone game that makes money so it is only right that Dota's content is also expanded. If there is one undiscovered potential for this genre to improve, it's a full single player campaign to introduce newbies.

How I thought of this idea is because I played Pokemon for a long time and every generation adds more and more complexity and mechanics into the game. Yet, Pokemon is still popular to both competitive adults and casual kids. In single player mode, players slowly learn how different type interacts with each other and how mechanics work with the help of a storyline. Even veterans can learn something especially with every new mechanics introduced every generation. By slowly easing players in with the help of a storyline, the learning curve is lessened. It draws both casual players for the story and the mini games in it and the competitive players for the competitive aspect of battling each other. Competitive Pokemon is actually being catered upon without making it too difficult for casuals and newbies.

This can be implemented in Dota as well in term of episodes with different heroes. Not all heroes need to have one. Naga siren could introduce the concept of illlusions and how they are typically used in a Dota game while keeping the explanation in context with the story. Every episode covers certain mechanics like the dragon knight tutorial covering last hits and items although it needs to be a bit faster than it currently is. Single player campaign needs to feel less like a tutorial and more like an actual game that is fun while still teaching. Every episode can be classified under beginner intermediate and advanced with different hero being feature in each episode and showing off mechanics in the form of a short story. One episode might require the player to juke using trees and cut a path to complete the story while the other teaches disjointing of spells and the whole objective revolves around those mechanics to ensure that the players focuses on it. It will be like mini games with stories that tells more about the world of Dota.

I honestly think Dota can still grow in playerbase with the addition of a single player campaign. Other than a short tutorial, none of the other dota games have yet to explore this idea because of the old and archaic belief that this genre is not meant to have a single player mode that stems from the limitation of the original DotA. The genre is well know for being punishing but I honestly think that's because no one has ever introduced a proper single player mode that makes the entrance to the genre easier. Removing mechanics is not how you make it accessible. It's how you eases players in to the depth of the game that makes it accessible. I think it would be worth it to try implementing this idea.