Low pop server / Server inactivity

[PariSexus]

^

While it wasn't officially a merge. This feature they implemented works really well. Wow also has what is called "Connected Realms" where, they group up certain realms (different than the battlegroups) and the players on these realms can trade amongst each other and be in cross server guilds. Another great feature.

[Aegis]

... shareholders and the like will view mergers as the game is failing...

You can't have shares in FFXIV, it's not like it's made by a small company with only one IP. You can have shares in SE, but shareholders in SE won't be paying any attention to things like patches or server merges, only revenue and subscription numbers (if they even bother to look in that much detail).

Sure if enough investors tell SE they would like to see a certain thing or another, they may try to accommodate but SE will never be forced into implementing something it doesn't want to.

There are no investors in XIV, only Shareholders in SE. The only pressure that can be put on Yoshi-P is from his immediate superiors (or us).