Hard to say how many have tbh...
I know I have the budget and knowledge to make a build to do all content but I never invested the time to do it.
Before I stopped playing I was mainly on my CoC Discharge character all the time and that was before the life leech nerf. I did all guardians but Shaper was new and I didn't know his mechanics (nor did many people back then) so I didn't bother trying.
I still have a few shaper sets that have been sitting in my stash. As for being able to kill him, I doubt I have any geared character right now that can kill him, so my guess would be that less than 10% of the players can kill him.
... but hey according to someone you just sit there and shoot projectiles and it's dead. No
CHALLANGE MATES