[AndMetal]

Here's where it's calculated w/ the bonuses (zone/bonuses.cpp):
around line 857

                        case SE_ProcChance:
                        {
                                //multiplier is to be compatible with item effects
                                //watching for overflow too
                                effect_value = effect_value<3000? effect_value * 10 : 30000;
                                if(newbon->ProcChance < effect_value)
                                        newbon->ProcChance = effect_value;
                                break;
                        }

Now, as far as ProcBonus, it ends up being calculated in the attack code also:
zone/attack.cpp, around line 3664 (in Mob::GetProcChances)

	ProcBonus += float(itembonuses.ProcChance + spellbonuses.ProcChance) / 1000.0f;
	
	ProcChance = 0.05f + float(mydex) / 9000.0f; //Base chance, based on dex + static chance to proc
	ProcBonus += (ProcChance * AABonus) / 100; //AA modifier in addition to normal ProcBonus from items & spells, percentage of base chance?
	ProcChance += ProcBonus; //Add the bonuses to the base chance
	mlog(COMBAT__PROCS, "Proc chance %.2f (%.2f from bonuses)", ProcChance, ProcBonus);
	return ProcChance;

So, if we use Jonthan's Mightful Caretaker as our example, the effect_value is 102, which ends up being 1020. In GetProcChances, we start with 0, then the spell value gets divided to 1.02. When we try the proc in Mob::TryWeaponProc (both with & without augs), also in zone/attack.cpp (around line 3674), we generate a random float between 0 & 1. Since 1.02 is always > anything between 0 & 1, we will proc 100% of the time.

I assume this is supposed to be a multiplier (200% = 2x as likely vs base, etc) instead of a direct mod on the proc chance. We should be able to do something like this:

	ProcBonus += float(itembonuses.ProcChance + spellbonuses.ProcChance) / 1000.0f;
	
	ProcChance = 0.05f + float(mydex) / 9000.0f;
	ProcBonus += (ProcChance * AABonus) / 100;
	ProcChance *= ProcBonus; //Multiplier instead of flat bonus
	mlog(COMBAT__PROCS, "Proc chance %.2f (%.2f from bonuses)", ProcChance, ProcBonus);
	return ProcChance;

If someone wants to try this and/or commit to SVN, feel free (I'm having some issues w/ Visual Studio after the change to zone.vcproj).

EDITED By Trevius: Removed stuff related to another thread