Ive been playing it some more but not much. Im figuring maybe later some of the more important NPcs will have some personality and characterization, or that dialogue will be more then just clicking to get a quest and direct exposition.
First two companions basically just say "hey, im going to join you." The second one, fighter in the bar, tells you in his second sentence about his falling with boss of the guild - all secret internal stuff of some mercenary company or something, because he discovered that his boss deals - directly with that ghost armor dude youre after and he will join you. yes, no?
All the companions have logical reasons for joining you both at the time, and for some of them, deeper reasons that are revealed later.
As for personality and characterization, I dunno what you want. My writing tends to be a bit "dry" but my characters don't have "extreme" personalities by choice, and don't necessarily wear all their ideas and opinions on their sleeves. Though that said, I'm not sure how you can miss out on the fact that Aneza tends to say, be compassionate, despises cities, etc. while Virgil reveres knowledge and learning as well as manipulation of others.
I go into a monastery, there is a reverend mother or something there, and three templar knights. give her a letter blah, blah - but dont go into the cellar. Right. You go see, zombies, undead - you go back, (Revenant boss) - cant say anything about it to anyone - Those three Templar Knights have no idea about anything before or after - nobody thought to ask them to maybe take care of the undead behind doors that are five meters away, or look into whats wrong with the cellar atleast. The reverent mother waited for you, delivering a letter from a criminal boss, to come in to even mention it. While there are three templars standing right in the church.
Why would they? Templars ? pft! In the middle of the main temple of a major city? fugedaboutit...
I think you're playing up the "delivering letters" thing a bit too much.
First, that is only one possible quest that starts you on one of the (mutually exclusive) questlines and is in no way required if you don't want to do it.
Second, it's justified as work to build the trust of the person you're working for, because there's not much reason to trust a new recruit into a criminal organization with super-sensitive info or complex, difficult tasks, is there? I'm sure if you went right to the smuggling, murder, etc. then you'd be complaining about how unrealistic it is that you're allowed to do so without gaining adequate trust.
If you speak to the Templars they specifically mention why they are there. You can literally ask this exact question and he gives you the answer.
Effectively the Knight-Commander pissed off his superiors in taking extreme action towards mages and was relegated to shitty duties in Arceris he wants no part of. In fact, if you are a mage (or have Virgil in your party) he outright has to restrain himself from insulting you, and he doesn't even offer you the option to do his quest if you are a mage, unless you can convince him otherwise using various skill checks.
Once again, I try to avoid dialogue that beats the player over the head with the obvious, and instead implies insight into the motivations of the characters involved.
As for not being able to tell the Templars about the infested undercroft - fair point, that was an oversight on my part (though admittedly a dumb one). Both those quests were later additions and I got much less feedback about them compared to other stuff. If I have time I might go back and tweak the interaction between both quests.