In source games your ping is really 100 + your listed ping due to sources netcode. I would suggest tweaking your rates as follows via console.
cl_updaterate 40
cl_cmdrate 66
cl_interp 0.03 to 0.05 (adjust to which value gives you better hit detection server to server)
The default for the first 2 values is 20 by default, and the default cl_interp value is 0.1 by default, which directly leads to your attempts to melee hunters to be "out of synch" which causes you to think you meleed that hunter before he pounced you, but you really didnt.
http://developer.valvesoftware.com/w...yer_Networking explains everything pretty well. L4D only runs at a 66 tic rate or lower right like tf2 does, so the tweaks are the same for both.
Hope that helps.