AbdulAlhazred
Legend
This probably already got discussed, but there are some odd points in this OP...Recently, largely I think thanks to the normally reliable Shannon Applecline, the idea that 4e Essentials should be counted as a separate edition has started to gain traction. I thought I'd have a look into the subsequent published books to see what happened if we treat 4e and Essentials as separate editions.
Heroes of Shadow was the first post-Essentials book and is an Essentials supplement. There is material in there that doesn't require HoFL or HoFK such as the Executioner and Vampire but 100% of the subclasses that aren't for new classes reference HoFx and 100% of the powers can be used by Essentials classes with just the books. (It probably didn't help Essentials that the Binder was so obviously terrible and the Executioner, Vampire, and Blackguard were all cool but mechanically way below the curve as was the necromancer and a warpriest domain; it's normally considered the worst 4e splatbook).
Heroes of the Feywild is a neutral supplement that spends more time referencing the PHB2 than HoFx. The new barbarian, bard, and druid variants can be used entirely out of HoFx but explicitly reference the PHB2. I don't think there is anything in there that requires either HoFx or one of the PHBs.
Heroes of the Elemental Chaos by contrast is a "both" supplement. There's a monk subclass and the Monk isn't in Essentials - and a Hexblade subclass when the Hexblade is only in Essentials.
The Dungeon Survival Handbook by contrast is a pure 4e supplement. There are things like Rogue attack powers in there that require a Dragon magazine feat to use with the Thief - and nothing that's explicitly Essentials.
Essentials was almost certainly intended as a revamp but fizzled hard enough 4e outlived it. And fizzled hard enough it only got one supplement.
First major point is that Essentials was a deliberately limited product. WotC announced it as 10 SKUs and stated flat out that there would NEVER be any additional Essentials products! So NOTHING post-Essentials is, technically at least, Essentials, and it is very clear that Essentials was NOT a 'replacement product', it was a line of supplementary 4e products intended to provide a limited subset of 4e which could be played stand-alone, but is 100% compatible with existing 4e material.
Obviously later supplements had to be developed with Essentials in mind as a thing that existed which many people would likely have. That complicated a lot of the development. My guess is that WotC also had a bunch of material that was developed in the process of writing Essentials which didn't make the cut, but which was potentially interesting and needed a home. Finally there are lot of things that Essentials opens up, like potentially more types of Cleric along the lines of the Warpriest, but which are not present in its limited set of books.
In the end, post-Essentials material is about 75% ignoring Essentials. Heroes of Shadow is probably the MOST influenced, it has several subclasses which are only useful with Essentials as well as a couple that can stand-alone but are presented in a fairly Essentials-like fashion. HotFW indeed pretty much ignores Essentials, I don't think anything in it references any of the HotFL/FK stuff at all. HotEC is still mostly written in terms of pre-Essentials stuff, except for the Druid subclasses and the hexblade elemental pact.
Honestly, I think the post-Essentials material is mostly quite solid. Many people have dissed a bunch of it, but both the stuff which references Essentials and the 'classic 4e' stuff is mostly GOOD. Binder is basically the worst thing post-E, and it is not actually terrible, just kind of unneeded and a bit on the weaker side of class builds. Vampires, the Blackguards, all the stuff in HotFW, it is all really solid. Some people weren't satisfied with the Necromancer, whatever. I mean, we all have our ideas of what things should be, but what it is works fine and makes sense. The HotEC stuff is quite good, all of it! Some things in these books are a bit experimental, maybe not really needed that much, like the Berserker or the Skald, but they work fine! I also disagree that the Vampire is an underpowered class. In fact, played and built correctly it is almost stupid overpowered!
And I think that really addresses the whole 'Essentials is an Edition' thing thoroughly. No, it is not. It is an expansion, much like the various 'Power' series books, just presented a bit differently and including a revised subset of the core rules. It has new builds of many existing classes, etc. but frankly you could just buy Heroes of the Fallen Lands and build characters using that and play them just like builds from any Power supplement or PHB. It is hard to call that a 'new edition', even if the classes and such are presented in a MILDLY different format from what was used in the hardback classic 4e books pre-Essentials. I mean, I can use any existing Paragon Path or ED with an Essentials class, even though they're bundled with a 'default PP/ED' and use any existing powers as well except where Essentials locks down my choices.