The devs attempted to provide an explanation in the patch notes, but I'd like to expand on that somewhat, perhaps to help clarify what I interpret their position to be. You don't have to agree with it, but it's important to try to see the big picture.

1. Different Skills for Different Situations

We're all familiar with the difference between PvE and PvP focused skills. Some skills are simply better in one environment and trivial in another. However, up until now, there has been little distinction between the various forms of PvE content in the game. What works for a trial boss fight will work for most everything else. It doesn't matter if the fight is going to be 10 seconds or 10 minutes. But with the changes to resource management, it has become prohibitive to use spamable skills throughout a prolonged fight. Does that mean these skills are relegated to the dust bin? No. In content that has shorter fights or PvP where they play into burst, they will still be used heavily. This creates a further degree of variety between how players approach different portions of content in the game.

2. The Cost for No Cool-Downs

The idea behind a skill cool-down is precisely to prevent it from being spammed. It is to disincentivize using just one skill so that the player will use a diversity of skills. Even in a cool-down system, you may still have resources which are consumed, but in a system without cool-downs the impact of resource management is the only means of curbing "spam" behavior. While this might not seem like a problem for dps skills like Force Pulse, it can be quite different when considering constant spamming of healing or shielding abilities. For example, if a Templar could infinitely spam one skill that healed everyone, why would he use any other skill? *cough* BoL *cough* In fact, this used to be a complaint, that Templar was boring because you could just use that one skill and nothing else. Yet over time the power creep of Champion Points and new gear sets has left the player base without much concern over resource management for quite some time. We all recognized this in PvP against unkillable tanks and in PvE where trials groups could run full bore damage with zero thought to regen. We knew something had to give. There had to be a return to actually managing resources.

3. Sustain Solutions

As the dev team attempts to divorce the idea of using spamable skills from long fights, it is important they remove any loopholes which would render their effort useless. That's why they hit so many areas of sustain. If they left one that allowed people to keep playing as they are, that would become the mandatory thing to do. So players must learn again to take resource management seriously. The most favorable form emerging seems to be the use of Heavy Attack weaving, as fully charged heavy attacks restore resources, and the new diminishing returns curve in the Champion system leaves players with points to put into Tenacity, further increasing Heavy Attack regen. Some players may opt for decreasing the number of heavy attacks required in their rotation by using regen or cost reduction jewelry glyphs, mundus stone, or gear sets. Others may keep their full damage build in favor of more heavy attacks to sustain it. Still others may look to skills like Equilibrium. And some may choose to go a hybrid route to utilize both sets of resources (though this will likely be less potent, it could still be relevant in non-high-end play). How players choose to handle resource management may differ, but everyone will have to take it seriously.

I'm not saying they got it exactly right. Some classes have it easier than others right now. But I believe this is the vision of the dev team and I, for one, think it is a reasonable one. Let's hope the feedback over the next few weeks helps them fine tune things so that their vision can be achieved without significantly handicapping particular classes.

I hope some of you found this helpful to think about.