Admittedly ANet has made some mistakes.
I don't mind that they give monks and assassins the ability to tank. However, even if you allow the tank & spank on such classes, you absolutely have to make sure it's not OPed. Afaik, tanking on warriors or elementalists never got OPed.
The big mistake you make here, is that players never used 55 or 600 for missions. With 55 you can't simply do your own thing because you die in 99.9% of areas. 55 is a pure farm build. It can not be used to normally play the game. So this build actually didn't create scrubs. The people who finished the game, always did so the regular oldfashioned way. Furthermore, apart from farming there was absolutely nothing else to do in Proph, back when 55 was first created.I don't. I believe that the refusal to nerf 55 monks quite honestly ruined the game. Creating these invincible farm builds which exploit the brain dead AI of pve monsters did one thing for a lot of players: let them make money while still being absolutely horrible players. They didn't have to learn how to be good, they didn't need to learn anything other than the 8 skills on the 55 bar, and could go out and do their thing.
This created a generation of scrubs who were so bad at the game, that when 55/600 farming was finally nerfed, that the majority of players were simply unable to get through most missions. So what does Arenanet do? Caves in and adds consumable items for them, and lets another, EVEN WORSE farm build run rampant - Shadow Form.
Besides, 55 was never "finally nerfed". It still works fine in select areas as it ever was: fine in select areas.
Let me please state that protective spirit is a core skill in PVP. Adding minimum damage to prot spirit would have literally destroyed the way PVP functions, since a.net always wanted protective prayers to be important. As such a minimum damage was never an option given that 55 was most heavily used before split skills were introduced. Furthermore it wouldn't have changed 600 with functions on a similar counterintuitive principle: low armor, high damage to be invincible.The 55 situation could have been solved ages ago by a simple addition of a minimum damage on Prot Spirit, but I don't know what the hell they were thinking when they created Shadow Form.
Even if a.net destroyed 55 by also destroying PVP with prot spirit, another build would pop up a day later, as it always did. Instead a.net chose to let this build live, because it was unique and could be stopped with 1 single skill if necessary. As such, there was actually never a reason to destroy 55. 55 was also never the only farm build, it lived alongside warrior farms, ele farms and ranger farms. The only reason 55 attracted so much attention was because of it's brilliancy in simplicity.
A.net finally caved at SF because they knew they could do two things: scare away all teamplayers in a very old game, or at least promote the one last form of teamplay left: UW farming. For this they indeed catered to shadow form. I don't like the build, I admit. But I'm also the first to admit that Shadow Form farming is VERY difficult. Scrubs can not and will not ever finish a single run with SF. Furthermore for SF farming you need a full team, skill, a good build etc which is actually exactly within GW's philosophy. A.net never destroyed SF, they carefully avoided that, but instead nerfed it by making it ever more difficult to use.
It's true that farming builds attract certain types of player - there's a whole microcosm of people who use it though and so we shouldn't leave them out of having fun in their experience of the game.
Funny thing is I took a run once from Doomlore Shrine and the runners (3 of them) all managed to die in what they said was a standard run for them. Luckily I had a back-up plan of a Shadow Form runner on my mesmer and went and rezzed them - but three runners dying - There's an argument there for just fighting through the dungeon.
Fun reading them type in 'team' their surprise at a mesmer holding Shadow Form - but pretty weak of them not knowing it could easily be done.
The build was simply spawned out of the fact that players are more creative than developers can imagine. It could've easily been avoided had prophecies and even later expansions been designed better. It's not hard to add enchant removals, touch skills, vamp etc. to most enemy mobs without any trouble at all.
All these extremely easy to pull off farmbuilds were part of what so easily inflated the economy, not to mention what has already been said. Loads of people skipped learning to play either through doing nothing but farming or by paying for others to play for them.
There is no reason vanity is supposed to be easily accessible when it's the single form of differentiation in a game. Therefore there's also zero reason for reluctancy to nerf mindless farming builds. On short term the economy might still suffer from the initial inflation and be more inaccessible to casual crowds, but on longer term it'll even out and prices will drop given no new gimmicks are available.
There's nothing different about simply clearing out missions or zones normally were dumb solofarm builds never available. It'd still cater to the people who enjoy being virtually rich. Think of all the original chestruns to the free chests that garuanteed gold drops. They needed no gamebreaking mechanics to do so. Taking out solofarming builds in no way removes the enjoyment of people who simply enjoy farming, it just reduces the efficiency enough so that the rest of the game can keep up better. I don't see how that's a bad thing when we still have these limitations in AI and game design.
As for saying there was nothing to do after completing prophecies. Why yes, that was the ****ing point. You ventured into pvp after learning wtf you were doing. There wasn't supposed to be anything else to do.