Executions fail to register, I have tested this time and time again. Most of the time the execution will record the event. Now some will say Lag, you just missed the points on the screen or someone canceled the action. I would be more than willing to accept those answer but that is not what I have found. I have found AOE heals can prevent the effects of Executions, and attacks that kill the executioner after the death of the executed and before the points show on the screen will prevent one from getting both the point towards total executions or requisitions. feel free to try it your self and see. There is about a full second delay between the event of the character death and acknowledgment of success.
The number one cause of execution initiation not registering for me is actually elevation. Someone on the stairs for example can't be executed unless you're on the same elevation As for execution completion not registering, there's usually two main causes. One is rage-quits. Someone who rage quits as you're executing him will sometimes get stuck in server limbo for about 15 seconds, and if that happens they deny you the 100 points for the execution. The other is the "all or nothing" nature of the animation; the victim isn't counted as dead until the executioner is free to walk around again, not when the visuals would dictate the victim should actually be dead However, I have NEVER seen a victim get saved by AoE heals like you're describing. Even in situations where they regain enough health while being executed, the ending of the execution has always killed them regardless and given the executioner the 100 points
While I rarely execute, except to conserve ammo, this is the one that I've encountered most frequently. So much so that when I've been downed on a stairs myself, I sometimes hang around rather than bleeding out to cause a nuisance to my opponents.
I find that the disconnect between execution effects / rewards and the animation itself is largest with the Howling Banshee. You can start walking away from the executed enemy before they finally die and you get your xp, it's quite bizarre.
I had a situation when I had time and chance to execute the same guy 5 times in a row. And no, I did not kill him repeatedly, he only went down once. He never actually died and I never got XP.
I once had a banshee execute me at least 3 times, while i was on attack on zedek, first time that ever happened to me I figured it was some sort of exploit animation cancel thing (since i was out of the way and keeping an attacker theoretically permanently downed is quite a good deal for a defender).
I was once shot down during an execution, rezzed by an apoth, and then managed to re-execute the same guy because a warlock had tried to heal him while i was down. It was quite poetic, really.
My favorite way of stopping an execute is via rokkit. Lets face it the downed ork player is probably screwed now anyway due to lack of ork heals so even if I duel the guy, pick up the friendly, he survives the 3 seconds of stand up cc,...he will probably die about 1 second later when a stray bullet grazes his giant hitbox. Whereas with the rokkit I get the kill and I do my teamates bleed out for him I will always forgive an ork that does the same to me if I'm being executed.