So often you see on a proc, "cannot be modified except by direct means." What is a direct modification then?
Direct means are when an effect specifically affects another effect or spell. For example, https://u.eq2wire.com/item/index/2998716036 (\aITEM -1296251260 1032767226:Hardened Cartilage Earstud\/a) has a Vampire Bane proc. One of the effects is that it makes other Vampire Bane procs stronger. This is a 'direct means' effect.
So just to be sure I have the concept right, another example would be Augmented Spite (from Experimentation). If you wear two items or more with it, the effect becomes stronger by some percentage. (It no longer stacks, I know.. )