First, GREAT idea for new players. Now, my suggestions:

1. Let players chosel a lvl1 spell. That's how it is in the game, why change it in the tutorial? Confusing and unnecessary.

2. Let players chose the spells instead of making them level up a certain kind of spell! That's how it is in the game, it also makes the tutorial more interesting. You still should recommend certain spells/build.

3. It'd be alot more exciting if another hero led through the tutorial instead of some creeps.

4. More interaction between heros: make it more dramatic. It's nice to have KotL around, but it'd be also nice if Razor'd fight back with spells or so. There's nothing bad with challenging the player, let them feel the tension. Some other heros joinig the fray to defeat the mighty Razor would certainly be neat aswell.

I'm aware that this is only a tutorial and that DotA isn't a game that is meant to be played as Wc3 with a singleplayer campaign, but a rich background story certainly makes it more loveable and rememberable.

Thanks for reading, love your work.