I was talking about the instance reserving issue with my sister, and it occurred to us, that part of the problem sounds like the servers are being overwhelmed by shear volume on reset day in particular due to the fact everyone is attempting to get in at once, because every ones tomestone limit as well as Coil limit resets at the same time. Obviously this is to keep thing easier on your end, so there is a consistent reset date, regardless of player.
Given this, while we realize you are also working to increase instance servers, we wondered if perhaps a better long term solution to mitigate overall stress would be to alternate reset days within each instance server group, so that different worlds reset on different days of the week. This way only ~1/7th of the volume is happening on any given day, thus distributing the reset load throughout the week.
To summarize, our suggestion is as follows:
Split each of the two data centers worlds up into 7 groups, 1 per day of the week trying to balance overall load of each server throughout the week, so that legacy are each on a different day of the week (as they have more people at 50), and similarly putting European servers on different days of the week, to distribute load during different times of the day as well.
So for the NA side something like:
Monday = Adamantoise/Balmung/Faerie/Mateus
Tuesday = Behemoth/Excalibur/Famfrit/Midgardsormr
Wednesday = Brynhildr/Gilgamesh/Hyperion/Moogle/Siren
Thursday = Cactuar/Goblin/Odin/Sargatanas/Ultros
Friday = Coeurl/Lamia/Phoenix/Zalera
Saturday = Cerberus/Diabolos/Leviathan/Shiva
Sunday = Exodus/Lich/Malboro/Ragnarok
From a technical side, having dealt with large scale database spikes, we believe this will drastically improve the overall reserving an instance problem as it relates to spike activity, while your addition of new servers will help with activity that is sustained.
Just wanted to put the idea out there, in case it hasn't already occurred to the developers.