Let's take these one section at a time, shall we?
The good news is the new defensive abilities the Guardians are getting. Shield Wall will allow the tank to take all the incoming damage targeted at another party member. And Fray The Edge is a new ranged single-target taunt that is stackable and has a chance of triggering a Fellowship Maneuver.
The bad news is some current defensive skills are overpowered and are getting tweaked. Shield-taunt will no longer put the Guardian at the top of the threat list, but will add significantl threat. And the Deep Breath ability that allows Guardians to prematurely end the cooldown of many of their skills is getting it's cooldown significantly increased.
There are some other tweaks, but the bottom line for Guardians in defensive mode is they are going to have to change their playstyle a bit. They have relied on some ability mechanics that are making their job too easy in some cases, especially in Raids.
Before the wailing and sackcloth and ashes get going, remember two things: the devs are trying to balance the game to make it challenging and every game does class revamps. No one hates you. Well, except that Minstrel that kept dying in your pick up group, but aggro control is everyone's job, right?
Read on for the really good news.