So it seems we are at a collision of the desires of these 3 groups of players:
1) Players who have enough time on their hands to have reached the highest tier of gear and find themselves wanting a sense of personal pve progression
2) Players who do not have the time to devote to maintaining a gear treadmill but want to enjoy the game and still have a sense of progression
3) Players who want to WvW on even footing without a grinding treadmill of gear requiring them to take a break from that to remain competitive.
These 3 arent mutually exclusive, but they present a problem in giving everyone what they want.
Solution:
The solution is already in the game and could be taken advantage of with a few tweaks to improve the mechanics in place.
First, FOTM is a great direction for both the first two groups, it gives a scaling difficulty of content that can be churned out quickly and easily meshed into the game.
Ill begin with WvW difficulties from gear treadmills. There are 2 problems encountered when creating a vertical progression:
1) It detracts from being able to focus on WvW
2) It creates an unbalanced playing field.
The solution to both of these is already implemented in SPvP. WvW should have a WvW specific set that can be purchased for free from the WvW vendors, the 7 core stat setups should be available in heavy/med/light versions to mix and match as you want with runes/sigils. This allows people doing WvW to not have to participate in the PvE vertical progression.
A fantastic tweak that could help balance in SPvP and WvW is to have a check for what is being hit with a skill, a player or an npc, and using x damage for one and y for another. This allows for balancing around pve and pvp independently when working with skills.
Now, as far as casual vs hardcore goes, I feel that Anet was really onto something with agony and FOTM. Instead of a vertical treadmill of stats, it seems the game would best be served by having specific environment stats to increase rather than increasing base stats by an excessive amount. Rather than have toughness and power increasing, you could have agony resistance, agony reflection, and some sort of stat that helps increase your damage vs npcs that use agony.
This allows players who are not hardcore to still be able to be useful in groups in open world or general pve content without having to keep up in gear: while still allowing for a progression for hardcore players in specific areas (post 20 FOTM or other such places where the debuff might not be Agony but might instead be Foefire or something.
Basically, I feel like Anet has done such an amazing job thinking in dynamic and lateral ways in so many areas, but might be falling victim to the pitfalls of other MMOs by thinking about progression in such restrictive terms as a gear treadmill.
At any rate, keep up the good work Anet, you are doing amazing, and I have faith in your ability to move forward in a way that will benefit everyone.