First off, I should admit that I've tanked on my shamans. My orc shaman tanked Deadmines when he was level 20, mainly because the group consisted of four people in cloth and my shaman in leather with a shield. This was back when shamans had abilities like Rockbiter (we still do, technically, but back in the old days Rockbiter actually added a high amount of threat and was useful as a shaman's tanking imbue) and Shield Specialization which made tanking feasible at lower levels. Enhancement was the tree of choice for a tanking shaman, as you didn't want any spells with cast times which could be pushed back or interrupted while you were taking damage, and Maelstrom Weapon wasn't even a twinkle in any developer's eye yet.
For a long time, in fact, the shaman enhancement tree was still reaching towards the same kind of hybridization we see today in the druid feral tree, with talents that could be used for tanking as well as melee DPS. As I'm sure a lot of old school shamans remember, this was in part due to the fact that Horde didn't have paladins and therefore shamans and paladins had to serve as mirror classes to each other, and since paladins had a (then more or less useless) protection tree aimed at tanking at launch, shamans had to provide similar utility. While neither paladins nor shamans were considered endgame tanks before Burning Crusade launched, it was seemingly the intent of the developers that either could serve in a five man in a pinch: I even recall going on a Zul'Farrak run with a level 47 shaman who tanked like an absolute fiend. Of course, it was simpler then: most tanks didn't really bother with defense before they started running the level 57+ instances like Strat, Scholo, or BRD/BRS, just stack stam and try and hold aggro as best you could with the limited tools tanking classes had. Frankly, shocks and Rockbiter were enough if you were motivated. It wasn't until people started raiding that the shaman tank started to become outmoded: most shamans in vanilla WoW endgame were healers first and foremost.
I first noticed the return of shaman tanks in Karazhan. At the time, Shield Spec still existed, but the change to Rockbiter had already left shamans dependent on Windfury procs (especially since Flametongue Weapon at that time didn't boost spell damage) and Spirit Weapons, necessary for the chance to parry so necessary for tanking also lowered shaman threat. Now, any enhancement shaman using the tree as it is normally used will tell you that Spirit Weapons threat reduction is a good thing. Today, in fact, it lowers all threat by 30%, be it physical or magical, very necessary with Maelstrom pushing the amount of magical damage an enhancement shaman does up. Still, the change to Spirit Weapons makes shaman tanking even harder than it was back in Karazhan, and as you'll note from reading my older post it was already a gimmick spec, requiring lots of PvP gearing (there simply is almost no +defense mail, and there wasn't then either) and a shadow priest to replenish the tank's mana. Today, at least, there are more options for replenishment, but at the same time, the shaman tank would be forced to choose between not being able to parry at all or losing 30% of his threat to do so. (And since Shield Spec is gone, he can forget about the extra 5% chance to block an extra 25% either.)
What the Wrath of the Lich King changes mean for any shaman wanting to try out tanking is simple: you will be at a severe disadvantage. As the post at Righteous Defense points out, you have to work around inherent limitations like having no taunt, no way to artificially increase your threat (the entire raid is threat capped at the level of the tank's DPS based threat, there's no threat modifier for shamans unless it's a negative one like Spirit Weapons) and no real way to regenerate mana to use to generate threat (although Shamanistic Rage could act as a mini-tanking cooldown and a nice mana regen ability, especially since you can use it every minute now, and Feral Spirit could help with incoming damage as well as threat from their damage). Basically, what was once at least tolerated in the enhancement talent tree is now totally unsupported: any shaman seeking to tank is going to have to build a cherry picked set of PvP gear and tanking rings, trinkets, a necklace, shield, possibly a weapon (the only tanking weapon I'd really say could take advantage of Windfury is a sword, unfortunately, meaning that a tanking shaman would have to choose between threat and tanking stats) which means he's going to have difficulty in catching up to other classes. You can look at Sharicasmi's armory to get a general sense of the kind of work you'd need to put in to do this.
In the end, despite the real and admirable work put in by shaman tanks out there pushing the class, I don't see a future for shaman tanks. With defense being removed from gear for Cataclysm (think the current feral druid model) the only way shamans would be able to tank would be if there was a similar crit reduction talent created for them, and I don't see that happening: when shamans were introduced to the Alliance and paladins to the Horde, the two classes were thematically uncoupled. No longer did shamans have to provide exact parity to paladins, and therefore, no longer did shamans need tanking talents and ability in their trees. I admire shamans out there working to do this anyway, and I find it shows a real ingenuity and love for the class (so much so that I'm planning on working up a tank set for my shaman before it becomes an impossibility) but I don't expect this is anything more than a diversion. Shaman tanking isn't in the cards as anything more than the work of a few smart, daring players.
Next week, we'll talk about leveling 41 to 69, getting past BC content and into the WotLK hotness as fast as possible.
Check out more strategies, tips and leveling guides for Shamans in Matthew Rossi's weekly class column: Totem Talk.