I understand that a game without fun gameplay isn't fun regardless of content but the same could be said of a game without content. Perfect gameplay with nothing to do is equally poor.

The thing i think you're missing though is that they are fixing the core issues while also adding content. This may mean they are both slower together than if they focused on just one however this approach keeps a larger number of people happy.

As i said earlier, the battle mechanics themselves are in a mostly finished state, aside from class/job balancing and BR changes. That doesn't include server related issues though, as that's an entirely different monster. I've never experienced a WS going off 5 seconds after a creature dies since launch.

Yes the system needs to be optimized and the net code needs to be reworked however that is not the current main priority. However that doesn't mean they don't have people working on it.

They have different teams so that no matter what the biggest focus is, other teams are always improving the other areas of the game.