ArenaNet announced the new set of global balance changes as well as those aimed at WvW and PvP. The latter two are mostly damage reduction but since everything got hit, these are not necessarily nerfs to any particular profession.
Guild Wars 2 is undergoing a balancing overhaul of sorts as the developers changed every profession in a single update. Overall, the global changes which apply to PvE, WvW and sPvP alike are aiming to get the less popular loadouts up to par with the rest.
The most important change is probably the one to Earth Elementalists which will cause them to stop grabbing aggro due to Stone Flesh. ArenaNet altered it to simply reduce a percentage of damage instead of granting Toughness, the latter of which causes PvE mobs to aggro more easily. Considering the balance pass is a major wall of text, we will not be posting it here but ArenaNet already did the heavy lifting and you can check the details on their announcement .
As for sPVP and WvW, players will now have to actually build for damage in order to be able to dish out the pain. Multipliers are going down across the board which will mean you will no longer be able to stack defensive stats and still deal major damage. Since damage output is going down for all professions, healing will be reduced to compensate.
Furthermore, longer cooldowns will need to be thought about before popping the skills. Impact of some long cooldown skills will be reduced in length so precision timing will be more important.
Instant skills will now have less of an impact as ArenaNet want the players to be able to counter the mechanic. Having overbearing abilities with no cast time could potentially ruin the fun for adversaries so now they will have a fighting chance. You can read about the changes in details on the PvP and WvW changelog .