I have recenty posted on renters insurance in the North American section here.
http://www.pprune.org/north-america/...insurance.html
This , I am afraid is becoming an area of fear , uncertainty and doubt just like rental car extras, that verges on exploiting the end user. My personal opinion is that I will only rent from places that cover the aircraft properly, don't act as sales agents for renters insurance, and doesn't attempt to blur or obfuscate the lines of responsibility for cover or attempt to make it the renters problem.
Yes, if you total the aircraft there is a deductible. Are the insurance company likely to come after you for anything else afterwards ? maybe if you were grossly negligent, drunk or whatever. Will renters insurance cover any of those situations? hardly.
At best, renters insurance is just a back door charging method to allow flying clubs to reduce their own coverage. At worst they are acting as agent for selling the cover, thereby taking a cut and making a load more things your responsibility.
I'd walk away frrom any rental that required this type of coverage.