I think its important to note that in hardcore players function almost solely on sound (due to the lack of HUD). This is why headphones and ninja are significantly more popular for hardcore matches! With that being said and the consideration of different players ability with different attachments I would make the claim that a suppressor is one of the MOST important attachments in hardcore strictly due to the quieter gunshot noise.
The muffled sound of a silencer and the lack of muzzle flash is significantly harder for players to locate then that of an un-silenced weapon, while the damage reduction caused by wearing a silencer is negligible. This gives you the same benefit you would receive in a non-hardcore game (not showing up on the HUD is the same as no noise in hardcore + the lack of muzzle flash) without the only draw back of the suppressor (lowered damage).
With that being said, I'm not sure if there is no 'pre-death' arrow caused by a suppressor. Even if that is the case, that is such a small benefit that I wouldn't even include it in the list of silencer benefits. The strength of the suppressor is the stealth.
Hope this helps!