The first time I smoked an ecig I had 18mg juice, and within 10 min of vaping I had a buzz. I continued to vape not thinking anything of it, and within 20 min I was on the verge of nic OD. I even had to get out of the car and let my wife drive because I was so light headed. But to your question, Its already known that ecigs are less effective as an analog at delivering nicotine. There are many threads on ECF on this topic. You are also not getting other harmful chemicals from analogs or other tobacco products that would cause a buzz. Also much like analogs, I myself stopped getting a buzz after my first few smokes when I stated smoking, so It might be a possibility that you have built a tolerance to nicotine. I also vape 24mg juice now, and chain vape all day without "catching a buzz". But I would rather not, I dont like the feeling of it.
Also I have tired the 24mg nic patches long ago for about two weeks. I was on a regiment of wellbutrin as well. Low and behold as soon as I would put the patch on, for the first 10 min or so I felt a buzz from the nic, but it didnt last long. I ended up still smoking a pack a day with the patch on and the wellbutrin, well that just made me have wired feelings, strange dreams, and a happy smoker.