I need to go back and tag past tickets, e.g. all tickets relating to "printers." But I can't search by that word in the Ticket View. So I'd like to be able to search by keywords, and then apply bulk actions to selected results in the Ticket View. 

Agreed. Find this a big omission. The current search field is very limited in that it's not simply returning a list in the ticket view where filters and other functions can be used.