Back in the first week of Cataclysm I had a lot of problems with heroic Stonecore. My guild did some runs, usually with 1-2 puggers due to not having enough 85s yet, and we wiped to Corborus a lot. We had huge troubles beating the adds quickly enough and the healer usually ran out of mana around the third burrow and we died. Today we did heroic Stonecore with a new 85 who just barely scraped by with the minimum 329 gearscore and we mauled Stonecore. We had some deaths, mostly due to people being extremely aggressive and unconcerned about dying, but we beat the place up easily. It is amazing the difference in difficulty between those experiences. Of course in the first week everyone was buying equipment they couldn't use and carrying around BOEs just to hit the 329 minimum requirement so we were really running at ilvl 325 or so while most of us now sit at 352. That is a solid 29% more stats on our gear, which obviously translates to a ton more health, avoid and damage. It is easy to see how that makes us better, as the dpsers end the fight in 80% of the time, the tank takes less damage and has a much bigger margin of error, both of which allows the healer to heal harder without running out of mana, which means we all live instead of die.
There are a lot of people complaining that heroics are too hard. They are complaining from the perspective of 'I got to 329 ilvl and the dungeon is still really hard' most of the time, and that is entirely true. Of course these dungeons are designed to be done with a minimum ilvl of 329, so everyone should expect that if you are barely even allowed to zone in that you better play damn well or you won't be able to succeed. Crafted gear, rep drops, BOEs and quest rewards, not to mention drops from regular dungeons can get anyone up to a solid 340 ilvl without ever touching a heroic dungeon or raid but it does take time. Most likely people are just bitter that they can't ding 85, hit the minimum ilvl and get carried by people in overpowered gear to massive rewards as they were used to at 80. Heroics just aren't that hard when you actually make use of all the upgrade paths available prior to them but the necessity to wait and prepare is not something the latter half of Wrath taught us.
As an amusing comparison, consider the difference between 'just ready for heroics' gear level in wrath and someone in half raiding gear, half heroic blues. We already saw in Cataclysm that difference is about 29% more stats, in wrath the curve was much, much steeper. A basic set of mixed 187 blues and ilvl ~170 greens give you approximately 120 stats on a bracer slot, more with the blue, less with the green. A mix of 213 raiding gear and heroic 200 epics has about 200 stats on a bracer slot instead, a 67% increase. Combine that with the fact that heroics in Wrath were relatively easier and it is obvious why heroics became a complete joke - it was very feasible to drastically outgear them within 2 weeks of hitting 80. The very act of making epics have the same scaling with ilvl as greens/blues has had a very powerful impact on reducing gear inflation, making sure that raiders have better gear but that a fully geared out raider in t1 content won't end up with a ridiculous 90% increase in stats from when they first hit heroics. In Cataclysm if you were geared in the same fashion, clearing all normal content and having all badge purchases you would end up with an ilvl of 359, a 33% increase over entry level heroic gear. That is going to mean that although better gear drastically reduces the difficulty we simply aren't going to see the level of disrespect for heroics we saw in Wrath and heroics are going to stay challenging for PUGs for a lot longer.