Hey Crimson. I realise this thread is 10 days old but I wanted to share my personal experience on this subject as my games have gone from no noticeable input delay to 3-4 seconds input delay (barely playable but extremely unfun) and 6-7 seconds at absolute worst; Playing with 6 seconds input delay is like trying to give instructions to someone who's black out drunk.
My ping hasn't changed, but recently my network connection has experienced a tiny amount of packet loss, about 3%. Now, no amount of packet loss is ever "tiny" because even the smallest number of packets dropped can really fuck up your day.
I mainly play 2 games, Dota and COH 2. Dota 2 is just about playable with packet loss as there are dedicated servers to communicate with which can minimise the effect of packet loss. You'll drop a few frames, sound queues, commands whatever but at least there's no input delay.
Packet loss in COH 2 however translated to huge input delay. I feel the reason the effect is so bad for packet loss is because of the P2P connection. I've played high ping COH 2 with no packet loss (against Australians and Americans) where input delay has been negligible, and I've played games against fellow British and European (heh, not for long Monkas) players with 3 input delay which played as if I was gaming from fucking Saturn. I'm not exactly sure why a P2P connection would cause this but then again I took not networking units at Uni
TL : DR Basically I'm pretty sure any amount of packet loss will massively jack up how much input delay you experience due to COH 2's lack of dedicated game servers.