This has bothered me for a long time too.
The instances that I raised are confined to secret society cases. They also involved weapons. The cases that you refer to may not fall into this category. Usually assault without weapons does not go down the path of murder, attempted murder or even manslaughter. The worst case scenario for the assailants are causing grevious hurt even when death occurs.
I see a pattern in the secret society cases thus my interest.
If I get your drift, loss of life must carry enforcement priority and the punishment must commensurate with the crime. The perception (and in reality) however this may differ and I feel that this is the case.
Interestingly Singapore has the toughest laws where violence is carried out in conjunction with a crime such as robbery, housebreaking etc where mandatory punishments is stiff. However if you decide to bash someone to death for staring at you, the Police, AG Chambers and the courts seem to be at a loss. I am therefore not surprised that the situation carries on.
I suppose a bank robbery where firearms are discharged followed by a movie getaway is more sexy to investigate, more sexy for the press to carve out the headlines and for the public to follow. The guy will certainly be hanged even though now one died or got hurt. On the other hand , someone bashed to death for wearing bad clothes and staring falls drammatically down the fashion ladder of crime, enforcement and punishment.
My guess is when a nephew or niece of a high ranking official falls victim, then the laws will be adjusted. When Seng Han Tong was punched in the 1st assault, they immediately increased simple assault to a drammatic 10 years jail with a condition for public servant or something along those lines.
Access to data is available via the courts but it will be challenging. A person well versed in research such as a academic or journalist is best at it. Access to the actual investigation files requires permission from Commissioner of Police. To my knowledge, only Sumiko ( and you know why) was ever given that permission. Even Alex Josey had only access to courts records when he wrote his book despite being old man's press secretary in the early years.