Hi back 
For me the .doc files are correctly recognized in caja as text files and opens by default with libre office. Maybe at one point you have done some config that mess up something.
You can insure .doc is present inside this file :
─[✗]─[olek@lenovo_apbook04u]─[/usr/share/mime/application]
└──╼ $cat /usr/share/mime/packages/libreoffice.xml | grep pattern
<glob pattern="*.sxd"/>
<glob pattern="*.std"/>
<glob pattern="*.oxt"/>
<glob pattern="*.sxm"/>
<glob pattern="*.sxg"/>
<glob pattern="*.xls"/>
<glob pattern="*.xlsm"/>
<glob pattern="*.xlsb"/>
<glob pattern="*.xltm"/>
<glob pattern="*.ppt"/>
<glob pattern="*.pptm"/>
<glob pattern="*.potm"/>
<glob pattern="*.doc"/>
<glob pattern="*.docm"/>
<glob pattern="*.doc"/>
<glob pattern="*.dotm"/>
<glob pattern="*.odb"/>
<glob pattern="*.odg"/>
<glob pattern="*.fodg"/>
<glob pattern="*.otg"/>
<glob pattern="*.odf"/>
<glob pattern="*.odm"/>
<glob pattern="*.otm"/>
<glob pattern="*.odp"/>
<glob pattern="*.fodp"/>
<glob pattern="*.otp"/>
<glob pattern="*.ods"/>
<glob pattern="*.fods"/>
<glob pattern="*.ots"/>
<glob pattern="*.odt"/>
<glob pattern="*.fodt"/>
<glob pattern="*.ott"/>
<glob pattern="*.oth"/>
<glob pattern="*.pptx"/>
<glob pattern="*.potx"/>
<glob pattern="*.xlsx"/>
<glob pattern="*.xltx"/>
<glob pattern="*.docx"/>
<glob pattern="*.dotx"/>
<glob pattern="*.sxi"/>
<glob pattern="*.sti"/>
<glob pattern="*.sxc"/>
<glob pattern="*.stc"/>
<glob pattern="*.sxw"/>
<glob pattern="*.stw"/>