Players were conditioned at the end of Wrath of the Lich King to mow through Heroics at lightning speed. Not only were they too easy to begin with, by the time Dungeon Finder came out players greatly out-geared the majority of these dungeons.
The reality is that it makes sense for Heroics to be a true and necessary stepping stone into raiding. They are more difficult at the beginning of this expansion's lifespan than they were at the beginning of Lich King. We like it that way. We want you thinking and trying new approaches through trial and error in order to succeed, just as groups do while raiding.
As new tiers of gear are released and new raids open up, Heroics will naturally become easier, but that provides little good reason for trivializing them now. This is true even if some groups -- particularly pick-up groups -- lack the patience, will, or teamwork necessary to succeed.
We prefer that skill and character power provide the edge in Heroic dungeons, rather than supplying simple boss fights where mistakes are so easily forgivable.
Will it test you to play at your best and communicate effectively with your group? Certainly. Should Heroic dungeons be tuned down so failure is rarely a real possibility? That doesn't sound like interesting design to me, nor would it act as a good catalyst for compelling, strategic, and social gameplay.
...
You might have to spend more time in normal dungeons than you did before if you want a very relaxing dungeon experience right now, before you jump into Heroics determined to succeed with ease. The difficulty of this expansion is on a different level right now, but it's still nowhere near the gap between five-player dungeons and raiding which existed in the original release, and to a lesser extent The Burning Crusade.
If you expect a quick, mellow run through Heroic dungeons -- which provide quite powerful gear given we're on the first Cataclysm raid tier -- this early in the entire lifespan of this expansion, you might want to consider collecting items and gear via normal dungeons and other means before regularly hopping into the Heroic queue. They're not super-unfriendly toward casual players, but they do require casual players to exercise skill and proper social/leadership skills.
