They should put actual MMO players on the development team.

[cloverkitty]

It is clear that a large majority of the people here have never worked in a Dev/Test environment.

Developers are coders. The take the blue prints that is laid out by the leadership (Yoshi, and above) and are given individual sections to work on.
- Network function
- AI
- Collision
- Engine
- etc

Graphics designers will work on the graphics and animations (individual groups will work on different set of graphics)
- Towns
- Dark Mobs
- Players
- Etc.

After all of those are are put together it is all pulled together into a "Build". Which if passes a sanity check is passed to test (also known as QA (Quality Assurance). This team will take various segments (and may even be linked to the teams of the devs that created the components putting their testing on the individual assigned components

Dev,Design, and Test do not play or use the game as a whole in making it.

Then it goes to the play testers who look for bugs, or functionality of the area/section of the game they are required to repeatedly test (levels, collision, effects, etc)

After all this the bugs are gathered and determined what is fixed, what is not (postponed, won't fix, by design, etc)

After all of the cuts and fixes and the product has met the bar for GA (general audience, or beta (public/closed)). Then it is reviewed by the management that set the directives on how the game is designed. If that clears then the product it put out for public beta or released.

That is about the extent of it. The amount of time playing an MMO or not would make no difference.
An opinion panel is typically part of the final review before release (although now a days they just use Beta for that).

Just my observations.