Yeah, the entire "storming the city" mission is really just a plot device to get Kirk and crew in a position where they're at Sybok's mercy.
I suppose if we really want to find some kind of rationale for the entire escapade, then the presence of hostages covers it. With the transporters non-functional, then maybe Kirk thought that a covert assault on the facility was the best way to ensure they actually retrieve the hostages alive. Using the shuttle or the Enterprise herself to do a ground bombardment, even with phasers set on a low-level stun setting, might be too risky for the potential health of the hostages.
Of course, then Kirk just... kind of forgets the 'covert' part of his plan, and storms the fortress directly.

I suppose if we really want to find some kind of rationale for the entire escapade, then the presence of hostages covers it. With the transporters non-functional, then maybe Kirk thought that a covert assault on the facility was the best way to ensure they actually retrieve the hostages alive. Using the shuttle or the Enterprise herself to do a ground bombardment, even with phasers set on a low-level stun setting, might be too risky for the potential health of the hostages.
Of course, then Kirk just... kind of forgets the 'covert' part of his plan, and storms the fortress directly.
