I know you were looking for experienced guys to respong, but I have to say these guys are right. Your club should be teaching proper defense. Also, your club sounds a bit like mind, with the exception that my club does teach defense. They will let you step in and spar from day one and that I have to say I don't agree with at all. I have only been there for one month and they want me to step in and spar already. They guys in my fight club think it's funny to beat on me on the mat, and I'm sure they can't wait to get the chance to do the same at stand up. I guess because I have been a weightlifter for 15 years and am big and strong. They are teaching me that my strenght and size doesn't mean much without any technical skill. I understand that now and just want to learn and actually had to go to the instructor and fill him in on this. I am a paying member like the rest and deserve to be taught as well and not play sparring dummy to the other fighters.
My point is you need to speak to the instructor and let him know how you feel. I'm sure unless he is a total jerk that he will listen to what you have to say and help you with your weaknesses. After all, if you enter into some MMA events and lose it will reflect upon his skills as an instructor. These guys want the best fighters to give their gyms a good name to attract more students. Good luck, and if he doesn't listen simply change clubs until you find oen that is right for you.