1. I think the engine rebuild will help with this, they were hitting limitations when it came to the current engine they were using. The tools are being developed as we speak, just look at the design documents.
2. If you haven't played in a while you really haven't seen the amount of content they added. The last few patches have added tons of sidequests for all levels, on top of the Grand Company quests for recruits, not to mention the quests you are able to get after you acquire Private Third Class. It's not a true fame system like XI had, but its similar. There's also the seasonal events, and the Seventh Umbral content (GMs roleplaying NPCs, Garlean invasions in certain regions, tons of stuff). The content of the game is starting to shape up quite nicely.
3. They are listening to the community, and fixing what they think has the highest priority first, which meant things that were fundamental to gameplay, which is why they took a step back on content for a patch or two to focus on fixing the battle system and adjusting the armoury system a bit because of the change. The fundamental gameplay hasn't suffered, and neither has any other part of the game. Everything is being improved at a steady rate, especially with the latest patch 1.19a.
As for the combat rewarding skill, I think they haven't quite hit that point yet. The UI and lag issues plague the battle system, but Yoshida has mentioned in several interviews since the 2.0 announcement that the client/server rebuild will make the battle system work the way they want it to, so hopefully 1.20+ will continue to bring improvements. I also think that once they release the job system, battle will feel a lot more rewarding. Right now its mostly hoping that you don't get fucked because your animation is locked, and hoping that you moved fast enough to compensate for lag. I know a lot of people complaining about positioning because of the Ifrit fight, but it will obviously improve as we inch towards FFXIV2.0.
Hopefully that will shed some light on your questions, all the information is pretty much from first hand experience, update notes and the recent interviews from all over the place.
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