Hello Spookie,
As a fellow security officer, I understand the frustration of having 2-3 D class rush up, kill 2 people and then die only to have them come back up and do the same thing while those security members are forced to sit back for 3 mins unable to help. But honestly the primary issue with the current system is that D class have no NLR while Security does even while in D block. While this makes sense from a balance perspective, it becomes problematic when you have 6 security and 10+ D class.
I think the easiest way to resolve this issue would just be to remove security NLR while they are in the D block area so that people can’t just rush up, kill 2-3 guards, respawn and kill 2-3 more guards while those others are unable to help. Because putting the NLR on only the weaponized D classes doesn’t stop them from bullrushing the door when security is busy with the D class with melee weapons.