Discord is independent of HLA and HLD. Discord reduces the resists and skills of the creature, where as
HLA and HLD lower the hit chance and defence chance of the creature. If you one of those effects is used on a discorded creature, its ability to hit or defend will be further lowered, than what it was originally. Discord combined with HLA and HLD is a very powerful combination.
For example: I have 100 Swords and the monster I am fighting has 100 Wrestling, I have a 50% chance of hitting it. If I discord (at GM skill) the monster, its wrestling will drop by 20% lowering it to 80 Wrestling. I will now have a 60% chance of hitting it. If HLD goes of on that same discorded monster, its DCI drops 25%, I will now have a 80% chance of hitting it. That is a significant drop in the monsters ability to defend itself. Use this
Hit Chance Calculator to see for yourself (you can also see how well the monster can hit you if you switch its data for the "Your" entries and your skills for the "Target" entries.
Stayin Alive,
BG