that's the reason why I regret xbow was conceived this way.
To my limited knowledge (some dilletantish archery and interest in medieval weapons) the historical x-bow was a weapon "any idiot" could use whereas bows needed more skill, so the average x-bowman was cheaper and thus more expendable than bowmen who often were trained in the art from childhood on.
The x-bow has the advantage that it can hold the bolt ready for a long time, while even trained bowmen can't hold a stretched bow for more than a few seconds, and every second makes your aim less steady. Bows on the other hand are
way faster, a trained archer can shoot once every three seconds: draw, aim, shoot, repeat. Try that with a x-bow, even with a drawing help (usually a lever or a rack-and-pinion mechanism called Cranequin).
So in my opinion the x-bow seems to be conceived quite fairly in D:OS, given that its additional AP cost is way too small compared to reality. Ideally, they should have divided drawing and shooting with separate AP costs and the ability to "store" a draw as long as the x-bow isn't switched out or put away.
Finally...do you see Witch fitting in the build (not counting what those builds say...I'd just like your opinion..)
Thank you anyway a lot for the time you're dedicating to my (lost) cause
My pleasure, I'm always happy to give some help after I received it myself from others when I had little to no experience in something.

Witchcraft also fits the Marksman by buffing one's damage or debuffing the target(s). The difference to Scoundrel is that it can be used on the Marksman by other characters, whereas most Scoundrel skills are self-only (since most scoundrels being selfish, after all

). So I would give Scoundrel to the Marksman character and Witchcraft to another. Since you plan to have a Geomancer, his/her Bless skill also is your friend (+30 to hit).
Have fun