Courtesy of the video description.The heroes / characters and ponies used are as follows, in order of appearance
-Donut Joe as Shopkeeper
-Derpy Hooves as Flying Courier
-Rarity as Sniper
-Spike as Dragon Knight
-Big Macintosh as Earthshaker
-Applejack as Windrunner
-Rainbow Dash as Storm Spirit
-Trixie as Lina the Slayer
-Twilight Sparkle as Rubick the Grand Magus
-Starswirl the Bearded as Invoker
-Philomeena as Phoenix (As of time of the release of this animation, still not released on dota 2 yet; but still a favourite hero in dota 1)
-Daring Do as Batrider
-Pinkie Pie as Gyrocopter
-Luna as Luna the Moonrider
-Lyra as Lion the Demon Witch
-Fluttershy as Enchantress
-Shining Armor as Omniknight
-Cadance as Chen the Holy Knight
-Celestia as Keeper of the Light
-Discord as Chaos Knight