When it comes to making game changes, in general, our intent is to react quickly to critical design and balance issues, bugs, and other problems that seriously conflict with our design intent through hotfixes. For issues which aren't as severely out of line, we plan to react in a more measured fashion -- through client patches. We have a patch coming (patch 1.0.2) that has been in development since the game's launch and is mainly aimed at addressing service issues. The first real game balance changes, outside of hotfixes, will be coming in patch 1.0.3. We expect that because the game is new, some other issues will arise that will need to be immediately addressed through hotfixes, but in general, most changes will arrive through patches.
Regarding the changes to Lingering Fog, Boon of Protection, and Force Armor: we determined these skills were simply more powerful than they should be, and we felt their impact on class balance and how each class was perceived warranted hotfixes as soon as we were able. However, we don't want you to be worried that a hotfix nerf is lurking around the corner every day. If a skill is strong, but isn't really breaking the game, we want you to have your fun. Part of the enjoyment of Diablo is finding those super-strong builds, and we want players to be excited to use something they discovered that feels overpowered. A good example of this is the monk Overawe rune, which many players have identified as being quite good. We agree it's good, but we don't think it's so far out of line that we're going to swoop in and hotfix it out of existence.
Inferno is intended to be extremely difficult, but with some specific skills, a few classes were simply able to progress far more easily than intended. This made the classes, which were about where they were supposed to be, seem very underpowered. It also created the perception that the classes doing well were intended to rely on specific runes in all their builds, and the other classes were just broken. This is the opposite of what's true. If any single skill or rune feels absolutely required to progress, it means that skill is working against our goal of encouraging build diversity -- and those "required" skills need to be corrected. We know these hotfixes snuck up on people, and it took us a day or so to communicate that they had gone live. However, our intent moving forward is that when there are circumstances where a hotfix is necessary, we'll communicate changes that could impact your ability to play your class through 'Upcoming Changes' posts in the General forum. Ideally, we'll let you know as soon as we even have the idea that we want to make that kind of change.