The Samsara is a really hard tip. On all really hard tips, you have to make sure that both the ferrule and the tip are completely flat. If there is any "rock" or unevenness, then the tip will come off.
We've put on thousands of Samsara's and the only issue we've had is either a hard miss cue, or we didn't get it flat.
We use Loctite Professional. Epoxy requires a film thickness to have bonding strength, but a film can be brittle if it gets too thick.
I'm not a fan of little scratches or holes. I don't think they do anything other than take away glue area. Of course, machining a pin will certainly help, and if you do machine a pin, then epoxy would certainly do well because there are areas for the film that would not carry the full load of the impact. I'm just not sure all that is necessary.
Royce