Ghostcrawler acknowledged normal and heroic difficulty dungeons were designed to be easier than what players are used to from their experience in World of Warcraft classic and Burning Crusade. Blizzard wants everyone to experience the dungeons—and that’s something the majority of non-hardcore players have wanted for years. This allows everyone to see the content and the lore. Heroics technically should be harder and more aimed to the hardcore raiding guilds (in my opinion).
Ulduar is going to be another story. Ghostcrawler said it will be hard. Nothing about the dungeon has been revealed yet. However, rumors are abound that the final boss might be Yogg-Saron, since that was Loken’s master. Time will tell if the rumors are true. There was a hint that more dungeons will be coming out via content patches.