Start: Stream of thoughts
Buy ret gear?
Belt has haste
Current belt is already decent and haste is bad
Why is haste bad?
Instant attacks are turning into an increasing portion of ret DPS. We used to be seal-judge and white damage was a big portion of DPS. Even without SoC scaling, haste was still pretty good. Then CS came and it made white damage a lower portion of DPS. But, at least for Horde, SoB also came and it scaled with haste. Auto-attack was still pretty significant. Now we have judgements that scale well and another instant, so auto-attack is a much smaller portion of DPS. This makes haste less valuable compared to other stats which scale with everything, such as AP or crit.
I realize that I am talking about haste as if it existed before BC. I don't remember ever seeing it, but let's pretend it did, just to create a more noticeable trend.
Is this trend going to continue? Will haste eventually drop to the point of affecting almost nothing? I see three conflicting forces in the fate of haste: space for GCDs, interactivity, and the purpose of future talents.
There are limited GCDs, so there comes a point when you just cannot add any more instant attacks. You can add more types of attacks, but you just cannot get past 2 per 3 seconds, limiting instants to a frequency of around 2.4 instants per auto-attack. Instant attacks would need to do ever-increasing percentages of weapon damage or stat scaling (which would have to exceed weapon damage) in order to gain ground against auto-attack.
In other words, there is a limit to how bad haste can become.
On the other hand, instants are more interactive. They make the game a bit more fun, giving something to do, options and tools. This suggests an increasing trend towards more instant attacks. There is still room for more instants, so more are likely to be added.
However new talents do not necessarily have to be part of DPS, healing, or tanking cycles. DPS could gain long cooldown abilities for damage increases or aggro reductions, maybe healing effects on their damage. Tanks could have more temporary mitigation, as death knights have. Healers could gain situational abilities like shields or guardian spirit. I think this is likely to be the future of talents: greater utility spells or long cooldowns which will not significantly affect the balance of instant vs. auto-attack damage.
Haste isn't in a very good spot right now. While it does do a good bit for auto-attack, it doesn't do enough compared to other stats to make up for them affecting all damage. Perhaps this will change, either by becoming cheaper or in some was increasing the value of auto-attack.