I took the scene a primarily in regards to 'Something isn't right here' after all you have a single defector showing up alone with no backup with a hostage wielding a strange weapon. Bajsaljen already believed that they had taken the Castrum far too easily so any rash action may have had dire consequences because they didn't know what to expect. So rather than rush in, they seemed to be attempt to bide their time to get a grasp on the situation. I doubt any of them were expecting a Primal to jump out of the sword and temper everyone. So even if from our perspective and hindsight rushing in may have been the best idea, the characters themselves were not aware of that.
As far as the WoL's action, well... your kind of butting up against two issues there... one is the limitation of action that can be taken in Cutscenes by the player character, there is simply no way that Yoshida and his team have the resources or time to adjust Cutscenes based on Job characteristics, so in that regard anything that requires the WoL of physically fight something MUST be done in a game play segment which depending on the cut scene could okay or very pace breaking and limits the scope of what can be shown.
The second is more character specific attribute of the Player Character falling into a specific heroic archetype as far as the general story in concerned. The WoL is very prone to protect friend and immediate allies over sometimes the long-term consequences. In this case it seems ensure Mikoto's wellbeing override the rest of the situation, mostly because the WoL wasn't exactly aware of Mijsa's plans at the time either, and when there isn't a specific plan, the WoL tends to just act in the immediate. Let's just say there is a good reason why the Scions and other groups in the games tend to make the major plans and the WoL is kind of directed in what the plan is, because left to their own devices they tend to follow immediate situation even at their own expense or with unintended consequences.