There is a problem is that a group that was unable to create an instance has no indication of when they might be able to successfully get one. What that leads to is a group of 5, 10 or even 25 people dancing in and out of the portal, hammering your server with dozens of useless requests per second. This must be creating yet more traffic for the servers.
If you don't get to the stage where you can remove the cap, would it not be better to implement a queue system as you do for battlegrounds and arenas? That way, once an instance has been requested for a group, they'll have an idea of how long they'll be waiting and won't need to keep hammering the portal waiting for the lucky window when the next instance can be created.
So it is important to implement an instance performance balancing feature to ensure stable and positive performance in raid and dungeon instances, which limits the total number of instances that can be created on a realm. Prior to this change, we were seeing serious issues in instances which greatly degraded instance performance, and in some cases, caused them to crash entirely.
This update instituted a load check that limited opening of additional instances. This will result in throttling of some instance creation where users receive the following message: "Additional instances could not be launched. Please, try again later." Ultimately, we felt that some wait time for players attempting to create a new instance was better than causing bad performance for all players in instances.
We are continually monitoring the realms affected by this and use the data we gather to implement further optimizations. Our ultimate goal is to work toward the removal of the limit.
There is some information about mana regeneration changes coming in patch 3.1, which is a fairly important piece of information to a large majority of players.
The goal is to have mana last about the same for all healers. We don't think many players would be that interested in a style where you heal crazy good for a short period and then run OOM. How classes manage their mana varies a lot, and we are making tweaks to it for 3.1 to try and keep them in line. For example, the shadow fiend needs to be more reliable.
The amount of base mana regeneration granted has been reduced 40%. We called this "Spirit" in the notes, since most player' associate OOFSR regeneration with Spirit, but in reality Innervate factors into the equation as well and we only lowered the constant, not the relative contributions of Innervate or Spirit. In retrospect, this probably caused more confusion than it alleviated, but mana regeneration is a fairly technical concept. 
The effects of talents that provide mana regeneration while casting have been increased by 67%. This includes: Arcane Meditation, Improved Spirit Tap, Intensity, Mage Armor, Meditation, Pyromaniac, and Spirit Tap. For example, Intensity and Meditation are now 17/33/50% mana regeneration while casting (up from 10/20/30%). For most DPS classes who never got much mana from OOFSR in the first place, the results should not be noticeable.
This should leave mana regeneration while casting (even the contribution of Spirit) relatively unchanged, but reduce mana regeneration while not casting by 40%.
Since Paladins don't rely on any of those abilities for mana regeneration, we lowered the healing penalty of Divine Plea to -50%. We are also likely to make Spiritual Attunement provide less mana for non-tanking paladins. We are not touching Illumination for the moment. Nor are we lowering the effects of Replenishment.