Could be that you update the spawn after every attack etc. so a lot of spawnpackets are send out from the server thus causing lag spikes because it'll keep delaying stuff.
Also could be the way you handle ranged attacks and what processing you do.
I had a problem with ranged attacks causing ping to jump to 1k instantly because of how it was being processed.
Current Packets from spelluse 06/08/2013 - CO2 Private Server - 4 Replies I wish someone send me the current packets SpellUse.
i have this packets:
public byte ToArray()
{
byte buffer = new byte;
Writer.WriteUInt16((ushort)(buffer.Length - 8), 0, buffer);
Writer.WriteUInt16(1105, 2, buffer);
Writer.WriteUInt32(Attacker, 4, buffer);
Writer.WriteUInt16(X, 8, buffer);