Hey, thanks for playing!
You're correct, there isn't anything new in the castle. The full update will add some collectibles to the castle, and some achievements for doing certain things/taking certain paths if those end up implemented.
There's no dialogue file for that character yet, so it tries to load it and fails. "Gracefully handle missing dialogue files in DialogueController" has been on the board for a long time, maybe it'll finally land in Edgewater (though that'll be too late for Shattered 2). Fortunately there's an autosave when entering the temple (you can also clear the dialogue through the console but that's obtuse and not really documented).
I wonder how much of what you're seeing with the enemies is placebo effect- I was surprised to hear they seemed to be acting more intelligently. I haven't made any changes to them for Shattered 2 specifically, nor any major changes to actor logic upstream. However, a few bugs and minor issues with actors have been fixed, so maybe they were being extra-stupid before and are now working properly.
I'm glad you feel the sidequests are worthwhile. To be honest, I was worried that most players might just skip them entirely, although that's one reason why I'm planning to add achievements, to kinda push people to explore and do the side tasks. I played with speeding up the sword attack way back when building A Dream of Valhalla, and it definitely felt better, but I felt a slower, more powerful attack made more sense for non-gameplay reasons.
That pull between narrative and gameplay and the inevitable compromises I had to make have been a recurring thing throughout the development process of this game especially.
The "four aspects" pantheon was partially conceived before the game was first released but there was just no way to incorporate it past passing mentions and that one texture.
I do like the idea of people who worship the "evil" Beast, and there's certainly a lot that could be done with the religion and culture of the Kingdom, but I have no idea how much of that will ever make it into a completed game.
By the same token, it would be interesting to explore the other cultures of the world, but most likely the East will never be developed beyond "mysterious foreign land we sometimes make reference to" for scope reasons. You never know, though. It would be the ideal setting for a game loosely inspired by East Asia the way "normal" fantasy is loosely inspired by Europe.
I do actually have one game in mind that's set in this world, but in a different part, different time, and not formally part of the Shattered series. We'll see about that one, though.
I'm hoping the next update (which will almost certainly be the big one, no in between steps) will be done soonish, but I've got a lot of stuff coming up IRL, so we'll see.