Blizzard's Dustin Browder explained during the BlizzCon opening ceremony that their game designers "challenge the genre" with Heroes of the Storm. He made sure to point out that games of this type were first created using the map editors that were shipped their games StarCraft and WarCraft.
Heroes of the Storm features three maps, shared experience, and is notably lacking purchasable items in game. No Shadow Blades, no Blink Daggers, no Infinity Edges. The games pace feels faster and more casual than its counterparts Dota 2 or League of Legends. This is congruent with design philosophy we've seen recently in Hearthstone.
Browder never used the words MOBA or ARTS during his presentation, using phrases like "brawler" instead.
Travis Gafford and myself will be doing another play test and will release a video on our intial thoughts on Heroes of the Storm later in the day.