Huh, didn't knew about that leak. It's true that the Elves were very weak in 6th. I was still playing HE back then. Of course, later they had to turn all of them up to eleven, when the 8th came out...
7th actually.
HE got armywide ASF and DE got armywide ASF and broken magic items (sacrifical dagger and reverse wardsave to name a few.)
They where both on top of the foodchain during the later half of 7th.
In my opinion:
6th had decent core rules and decent internal and external balance - from what I can remember. When I got into WFB 7th was just around the corner, so I didn't get that many games under my belt before the transition to 7th, not to mention that it's what...10 years ago now?
7th had good core rules, and was good (relatively) internally and externally for the first half of it's existence.
Then all of a sudden, the powercreep took to new levels with the introduction of the riddicously OP Daemons of Chaos, and many of the AB's that came after followed suit: VC, DE and HE to name a few. After that 7th became a mess of unbalance.
8th had...decent core rules, but I never really liked them that much. 8th quickly turned into a edition of Hordes and OP magic, which was one of the reasons I never played 8th that much after the first months of release. I liked the fact that infantry was viable again and not just a block of static CR, but the game encouraged hordes way to much. The internal balance in the 8th Ed. armybooks was also laughably bad in some of the AB's, like GW stopped trying. When 8th was launched in 2010, I owned 5 armies: High Elves, Wood Elves, Dark Elves, Empire and Warriors of Chaos. When AoS was launched in 2015, only two of theese remained, namely Wood Elves and Empire. Dumb as I was, I also sold of theese two after AoS was launched (I don't like AoS, let's just end it at that), so now when 9th got me back into the hobby I had to restart all over with Empire and Warriors of Chaos....
9th Age (it's not Warhammer in name, but it's essentially 9th Ed.) is a continuation of 8th Ed, and has led to the game being in a better state of internal and external balance than it has ever been in since I started. For the first time more or less every unit inside the different AB's is viable and serves a purpose, and all armies have a good chance of beating eachother, assuming equally skilled generals.
Apart from this, 9th Age has fixed alot of (but not all) the things I disliked about 8th Ed - magic is still strong but it's not OP. Hordes are still a thing, but they're rarer due to alot of unit's having a max cap-size that discourages hordes (like 30 or 40 for instance.), middle-tier monsters like Manticores, Griffons and the like are finally viable, and cannons aren't laser-guided anymore.
Granted, it's not perfect, but it's a damn good game and an improvement over 8th in most regards. It's also a living rulebook, where things that are considered too good/bad will get attention, and where new units, even armybooks (like DoW) can be seen on the horizon.
This is one of the main reasons why my gaming-group has moved on from 8th (not to mention 7th or 6th) - if you consider 8th the best edition, then great, more power to you - play it. But at the end of the day, it's a edition in total standstill, where the AB's, units and rules are where GW left them, and you better like it, because it won't change.
A World of Warcraft-methaphor would be abit like asking Blizzard to reinstate vanilla servers. Many "veterans" would love to play vanilla again, but after awhile most of them would probably get bored and move on, since there's only soo much you can do before the game is "completed" without a constant input of updates and new content.
And please, don't see this as me bashing/hating on 8th - see this as me explaining why I and my gaminggroup have moved on from 8th.