It's a shame to hear stories like this, especially considering there is no solid data behind these revenge evictions.
While it's without any doubt that most landlords find repair request a nuisance, I find it odd that they would risk losing thousands of pounds with a potential void period and letting fees, instead of spending tens or hundreds on simple repairs.
Lettings agencies are getting more efficient with reporting systems like FixFlo (http://www.fixflo.com), which uses a comprehensive set of pictures for tenants to pick what the issue is. For agents, it seems this simple piece of tech completely removes the pain of phone calls and emails, just to figure out a handyman needs to go around and tighten a bolt.
If landlords made it mandatory for tentants to report issues through a Fixflo-like system, maybe these stories would become a thing of the 20th Century past.