The NPC/player teleport trick isn't very practical, as you can only move to another player's location, saves you like... a 2-3 second run AND you can only do it when there are NPC's around; thus rendered useless in the harder parts of the game
The monster teleport thing is kinda useless too.. because monsters are usually grouped near each other anyway. Since you talked about adrenline, I'm assuming you have to use a Warrior, meaning.. warriors can already take a lot of hits. Kill one monster, run to next, kill, rinse and repeat. Overall, you save yourself time by just killing normally -- since you won't teleport each time you try it and the monster only dies *once*.
In my opinion, I wouldn't call these "teleport exploits"... but just as minor glitches which you've stated in your own post.
[Edit] I just re-read your post and saw the bit about teleporting from merchant to other NPC's in the game -- this could potentially be useful, will have to test that out.