Unlimited pathfinding?
Well, you can always run away, and let the monsters die with distance/time, or put up fences, etc.
The bigger issue is that unlimited pathfinding, without "can you even be sure that there is a path", can quickly turn into a CPU/memory nightmare on the server.
As for "Attract all mobs in range", that's not necessarily a bad thing. It does mean that if you can do a good scratch to someone, and that person does not have backup prayers or other healing options handy, they are in serious trouble / have to wall off. So the whole issue of "The fights will go on forever because someone can disengage, heal, and recover/return" is less of a problem -- since both players have to worry about mutual damage below 6 (Q: Is that 6 hearts, or 6 health? 6 hearts -- you start bleeding at 45% damage taken -- is fairly early/quick), both players have a desire to break off. If anything, arrow sniping / traps become a better option than normal -- bow against a sword, with distance between them, goes to the bow wielder.
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Wait, GasCraft? Isn't that the mod that just makes mining more dangerous, with gas pockets that can explode from torches, and no real benefits from the gases themselves?
No you're thinking of the Gas mod in BnB. This allows you to create gases and use them as weapons. No naturally spawning gas.
Afte reading what Shazam said, I think I'll be removing most mob mods, including Zombie Awareness.
As for generating ores using COG, I'd personally rather use TPPI's method of Ore Gen and increase spawns, but I think it's import others have their own say on this.