It happened to me today and was wondering if it's happened to anyone else.

If 2 of the 3 slots are filled on an elite and the 3rd person just needs to "tap" it to finish it off, only the first two hitters will get the reward. When it happened to me, I definitely got the last hit and should have got a notification about the kill. Only the other two hitters got notifications and the 3rd hitter (me), didn't get anything. I checked my cargo to see if any reward was there and it wasn't.

Was this intended to happen or is it a glitch?

Not sure if intended or not but it is a very old well known situation.

You won't get a reward from any elite if your one and only shot on it is the kill shot.

Yup, the kill shot isn't counted, so if your hit killed it, you won't see your name doing any damage. Similarly if you're in 4th on a 3 man and you kill it (but that damage would've moved you into 3rd) it doesn't put those damage points towards your total and you will stay in 4th. This is why so many legions have a rule against soft locking.

Since I have not seen anyone note this directly:
Any action that gets your name on the damagers list (whether it be a debuff or a hit does not kill it) will deem you eligible for the reward. In short, if you see health that may not last 2 hits left on an elite, and you want the last slot, shoot an EMP, Drannik Saboteur, etc on it, and you can get your reward.

I have seen a bug with NPC's a few times

Last hit, the one that kills it doesn't count for total dammage
so if you only hit it that one time and kill it, no you dont get a reward - as the system doesnt registrer that you did anything vs that NPC

but if you use an artifact or ability on it first, you will be listed as having done 0 dammage
and that can actualy get you a reward from it even if all you did was hit it with a EMP Sphere or simular artifact