: I think they were overused.

: And I learned that teleporting enemies cause story problems. I remember, in
: Spartan Ops, just after I killed the last promethians atacking Infinity...
: a voice over comms said, "That's the last of them".

: How did the voice know? They came in waves, they can teleport, they don't
: stay dead and I had JUST "killed" the "last" one.

: I know the voice actor is reading the script but how did the character know?

Energy surges, or summat.

But yeah, the question of when they port in (and why they could port to Infinity but couldn't other times) raises more questions than you want to answer.