I think you are not making any sense whatsoever. First, who ever said being a tank meant you had to tank in a raid, and only in a raid? You can use tank specs for dungeons, soloing, leveling, achievements, old content runs, not-so-old content runs (say of previous current-expansion tiers), alt runs, even some PvP usage ("AND WAIT, THERE'S STILL MORE...").
And trust me, being a tank/healer will get you raid geared for DPS much, much faster than waiting in queue. That, or you'll have to kiss major ass to hope to get a queue buddy. Hardly a "compelling design." You seem to think that being a DPS means you only ever DPS in LFD, and being a tank means you must be the main tank of your guild - no sense.
As put by various people, a remnant of the original "tank spec" idea is in the glyph, and you can ask people who use it whether they think the 4th spec would be "so far out on its own" - most people would disagree with you here.
There is, it's Fury Ward. You only need to make it scale with SP (vengeance), and add an additional Fury dump that gives a more primary form of damage reduction.
1) You missed my original point completely. Some of the tones make me think that the "fear-mongering" crowd seem to think that making a tank spec would somehow mean that we'd have to replace all of the specs with tank specs and leave no DPS ability left (hence the "replace the all sword icons with shield icons") when this is not what anyone is intending whatsoever.
2) You're contradicting yourself. First argument is that nobody will use tank specs because "they aren't needed in raid" - but if they really aren't needed if you're not a MS tank, then why are we suddenly being "forced" to use tank specs?
As put, plenty of people are playing the DPS specs of a class with tank/healing capabilities and are doing fine. Plenty of priests are playing holy/discipline and are doing fine. Plenty of people just play tanks without off-specs and are doing fine. I can hear out some arguments about why adding in extra specs will make the class work, but only hearing "People will hate being 'made to tank'" is pretty ridiculous, considering the biggest likelihood is that they won't be made to do so at all.
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P.S. The majority of people I know who do in fact prefer pure DPS classes simply like to DPS and do not care for tanking or healing. They are not, however, afraid of being asked to tank or heal because their guild knows that they just prefer to DPS (amazing, they actually communicate what roles they like to play with their guild).
In this case, what would said people be losing if a spec is simply added without taking anything away?