Ok, so you remember how Titanguard, the 75 stamina weapon enchant, disappeared from 3.0.8? Apparently, that was intentional. Ghostcrawler spoke out yesterday on the rationale for removing it. In short, it was just too good. That 75 Stamina would have made it far and away the best tank enchant, and would have locked them into creating higher and higher tiers in future patches and expansions so tanks wouldn't just stick with Titanguard and be done with it. Not only would this lead to less variety in game, but the developers would be stuck specifically designing future encounters with the assumption that every single tank had that extra 75 stamina.
Blizzard's certainly shied away from making certain enchants too powerful before. For example, the Crusader enchantment was given diminishing returns after level 60 specifically so it wouldn't overshadow any other weapon enchants. With that in mind, this move does fit in with Blizzard's modus operandi. And if nothing else, it's good that this was nerfed now, before it made its way onto the live servers. While some tanks may not be happy with the outcome, this is certainly an instance where the PTR testing process worked.
Death Knights will still get to keep the +2% stamina on their Rune of the Stoneskin Gargoyle, in part to make up for the lack of a shield and a solid defense sigil. Ghostcrawler also did not rule out the possibility of future tanking enchants, but only if they could find out a way to prevent the same problems that caused them to take out Titanguard.