They literally said it here:
Hello! We have seen a lot of questions about the talent system preview, here and in other feedback, and want to start answering what we can. Note that it’s still too early for a lot of specifics (including, we can’t post complete trees yet for people to peruse). There is still a lot to discuss about our approach and goals for the system.
Primarily the latter. We’re still experimenting quite a bit with drafting trees, but currently the majority of nodes are 1 point, with some 2-3. It turns out …
In addition to Sigma’s thoughts above, We have gathered several questions (mostly from players on Twitter asking Desvin). Here are our answers to those:
When do talents become available?
The talent system becomes available at level 10 when you choose your Specialization for your class. For the Evoker, because they are starting at a higher level, the talent tree will be made available at some point during their starting experience.
How many talent points do you get, and how do you get them?
…
Surprised nobody linked to those posts yet…
Specifically:
We are currently trying to focus as many combat-altering abilities as possible into the new talent trees. This can include things such as movement abilities, interrupts, dispels, hybrid healing options, defensive abilities, etc. Our goal is to set up the trees and paths so that there opportunities to choose between different types of utility, but not to, for example, abandon all utility choices entirely in order to maximize your DPS. If you choose not to have an interrupt, it is likely because you traded it out for some other type of utility or CC that you believed would be more useful in the situation. The inverse is also true—specializations that do not have a certain capability in Shadowlands (such as an interrupt) may be able to obtain it by giving up something they currently do have.
Personally, I’m super not a fan of this approach. It means you can have a ‘wrong’ build too easily. A mage isn’t going to forget how to cast firebolt just to get an interrupt. Talent trees to me should be 80-90% passives with potentially a capstone active. But putting core gameplay abilities in the tree just feels bad to me. It’s one of my main criticisms of what we have now and what I was hoping desperately they wouldn’t keep if they moved back to traditional trees. The other aspect I’m not a fan of is the fact we still have 38 classes in effect. Instead of 13… because they are still hyper focused on specs.