You forgot to add that Chekov, a former security officer knows nothing about the Enterprise's weapons alarms or how to conduct an investigation.
But they don't all act out of character - Rand was still an air-head and she cried over Kirk.
Trek has never had a very appropriate approach to telepathic intrusions. Babylon 5 handled the subject far better. But this approach is symptomatic of a lot of American story-telling in the 80s and 90s where interrogation techniques are pretty much torture and abuse. Hopefully the generation of writers who have lived through a decade of CSI might see better ways of getting the truth. I was appalled in Lost when so many of the characters stepped back and encouraged the torture of a man for information when in fact a few simple questions would have sufficed (and eventually did). If Jack Bauer were interrogating Valeris you can bet he'd have had her pinned to a table with a laser scalpel poised over her eye.