Ok, I usually find a looper or two every now and then, but what I do is focus on them without tunneling every time I find them again, and maybe because of luck but that hasn't stopped me from getting the other 2 or 3 kills as well...
But, yesterday I went up against a looper in the farm (I don't remember the name of the map) and the loop inside of the structure of a destroyed barn made me loose a lot of time and I could only get two kills, one of them being the looper.
Any advice? I'm not a regular player, I'm a rank 8-10 almost all the time... And yes, I tend on focusing on the looper to punish that behaviour
EDIT:
There, the answer was simple, I changed killer... Slow killer means avoid looping and go get the others, fast killer with helpful habilities mean stay on the looper and punish him. Freddy is awesome for this now, also the huntress and the clown.