Who the hell goes to arena as an enhance shaman?
There are 2 2200+ rated ones I know of.

Shield spec won't help you when you are dropping 20-30% damage because you are in leather, which if you are good, you will be in mostly. They are finally starting to put Mail in there that is better than the leather for us at the same level. And not by much. Even if you are in all mail, you won't survive more than 2 hits even with a shield. You have the lowest HPS of a melee class and worst mitigation. A rogue pops evasion and can survive being targetted by simply not being hit. We aren't doing that.

He took mental quickness. Why even bring it up like he didn't?

If you are being beaten on in PVP or PVE you have 1 choice, outDPS. If you cannot you are dead, our heals aren't beefy enough to handle trying to outheal someone. If you are raiding and it turns on you, you aren't outhealing it. You are just going away. See shield spec.

Sheild Spec is terrible....

Sorry but most of what you said is either incorrect, irrelevant or only an issue to people with no clue.

Exhibit 1: 'Shield specialization can actually be better than ancestral knowledge, it gives you more damage mitigation when you pull aggro off of tanks (Any Good Enh Shaman knows how easily this can happen), or when you are being focused on in arena.'

Shield specialization is of no value what so ever to a raiding enhancement shamans, it is of some small value to a Arena spec but tbh not much as it is only situationally useful. 'Any good Enh Shaman' wont pull agro from the tank, here is a pro-tip: don't hit the mob until the tank has built up some agro and even then you can ease up by not hitting SS... less dps from a living shaman>no dps from a dead one.

Exhibit 2:'Improved reincarnation is good for raiding, but Mental quickness in the Enh tree makes your shocks a lot more beefy, and is definatly worth 3 points.'

The spec linked in the article has both of these things... why even bother making this comment?

Exhibit 3:'For PVP builds extra point should usually be funneled into anticipation, gives straight damage reduction. Also, for PVP and PVE 4-5 Points in Healing Focus, actually lets you get a heal off while being beaten on!'

Any 'pvp build' that focuses on Enhancement talents is a wasted pvp'ing shaman. Enhancement is by far the weakest of the 3 trees for pvp. My advice, dont bother... respec elem if you want to pewpew or resto if you want to heal.

lol, shield spec? Are you serious? If you pull aggro in a raid blocking for 120-150 isn't gonna save you, you're dead. This is why we take imp reinc aka shaman vanish.