So the latest game update 2.50 removed the attention meter spikes and makes it nearly useless (depending on the view angle)
My suggestion is not only to bring the spikes back, but also divide it in 4 blocks:
The 1st block shows the player he´s in the line of sight of an enforcer. Once the half moon shape is filled, the outline of the 2nd block will appear.
If this 2nd block is filled, the outline of the 3rd block will appear. The npc get´s a question mark and looks at your last known position for a few seconds.
If the 3rd block is filled, the outline of the 4th spike shaped block will appear. The npc get´s a question mark and walks towards your last known position.
Once the 4th spike shaped block is filled, you´re spotted.
In hostile areas the attention meter turns red.
I think this would make the attention meter much easier to understand and the gameplay mechanics better to use to your advantage.