It's interesting how many different types of issues the label social anxiety covers. That's one of the reasons why certain things work for some but not for others.
Exposure can be useful but you have to make sure that you don't overdo it.
Have you tried any gradual/graded/systematic desensitization? It can be done as real or imagined. Here's a link that talks about imagined version and has a lot of useful extra notes to improve the chances of it working.
I've heard the following statement but didn't find it matching my experience.
A recent book I read, mentioned these ways to become anxious.
1. Danger is present or near, in time or might be coming in the future
2. Internal trigger stimulus (body sensation)
3. Triggered by thoughts or memories
4. Thoughts or memories (existential dread) about meaningful life, inevitability of death, difficulty of making decisions that have moral value.
If someone suddenly threatens you with a knife or gun, that fear is about as much being in the present as it can be. Most of my issues were also like that - (e.g. standing in line or giving speed, etc) as my mind went blank often in the higher intensity panicky situations. An improv class illustrated it really well. When I had a mind block, our teacher said "Don't worry about anything. Just say the first thing that comes to mind". I wish that had been my situation ... but I couldn't think of anything. That mind block happened quite a few times, but there were somewhat more times where I was able to come up with something and make people laugh.
Sometimes attention diversion techniques can work but if the fear intensity is too high, then it's better to focus on desensitizing the fear trigger (as mentioned above) with other approaches.
Firstly, I agree that not over-doing it with exposure therapy is an important point. My first Toastmasters event was way too much for me to take at that point, and it was an important learning experience for me.
I didn't see your link about gradual/systematic desensitization, but judging by the wording I'm assuming it is just slowly working up to more difficult exposure therapy tasks.
I did that to some degree starting with relatively easier tasks, like wearing ugly clothes to the mall, then worked up to giving speeches.
Recently I came across a TED talk on comfort zone's, and think I'll just do those from time to time, to continually improve my self confidence and continually reinforce caring less about others opinions.
It probably depends what we consider 'present' and 'future'. If someone is standing across from you with a knife, presently you aren't really being hurt right? You might be worried that a few seconds from now you will be stabbed causing some kind of problems in the future.
Imagine, you could take a snapshot of facing a knife wielding attacker and just stay in that moment forever. You would eventually come to realize that this isn't currently a scary thing since the attack in the future isn't coming, correct?
My experience with improv is that, yes I felt anxious during the improv causing some blank moments. However, I think that is because of worrying about the future. From here on I'm just going to use the word 'speech' to represent 'improv'.
When I'm going up to give a speech I'll worry about the future, thinking things like "I hope my mind doesn't go blank causing me to emberass myself in front of people" and additionally, once that adrenaline starts pumping I''ll think things like "Oh God, it's happening make this adrenaline stop!".
Once I'm up giving the speech I'm anxious, but that is because I was worrying about it before hand, working myself up into a frenzy. When I'm in the moment giving the speech and not in my head, the anxiety levels drop. Sometimes during the speech I'll have this weird 3rd person thing where I'm talking but also thinking at the same time, and that's usually when my anxiety levels start creeping up again.
If that speech was 100% in the present there would be no thoughts of others opinions before. There would be no thoughts of others opinions during. The only thought would simply be "My job currently is to recite my information that I've prepared before". That job by itself isn't adrenaline inducing, it's all the other things surrounding it that cause anxiety imo.