Eleven dives really isn't much diving.
The point about Rescue Diver is that you need to have enough skills and experience to be able to assist another diver. More than that it's about preventing problems in the first place and being competent enough to not become another casualty. Much of this is noticing when something's wrong -- looking at a random diver and seeing that, say, their drysuit's not connected or they're looking "wrong".
Of course we're all different and some people naturally pick up skills very quickly whereas others take some time to absorb and perfect the skills; some never master the skills.
My real concern about achieving RD in that time is the syllabus coverage and the time to practice, really absorb the skills, be self-reliant and develop your own opinions. One has to assume that you had an amazing trainer, great conditions and you have the innate ability to learn this.
For me, RD took considerably longer than that, especially with the beasting of a final scenario rescue in poor visibility to search for a missing diver in a current, assess them, bring them to the surface and all the other skills. It was a hard but very fulfilling course.