I dunno how to phrase it correctly, I just leave it here.
About increased extra damage from Critical Strikes
"This modifier is multiplicative with modifiers to the player's damage or critical strike damage" - this statement is wrong. Only extra damage is multiplied (proof - ). I mean, if one have normal hit of X dmg and crit multiplier of Y%, than his crit damage equals to X (his normal dmg) + X*(Y/100%) (extra damage from crit). And modifier Z% increased extra damage from Critical Strikes increase his critical dmg to X (normal dmg remains the same) + X*(Y/100%)((100%+Z)/100%) (extra dmg increases).
Elemental Overload makes this modifier useless, because it makes Y=0.
Lets assume character to have 1000 dmg, default crit multiplier (50%) and 20% increased extra damage from critical strikes (from assassin's mark). His crit dmg against non-cursed enemy is 1000 + 1000*0.5 = 1500. His crit dmg to cursed one is 1000 + 1000*0.5*1.2 = 1600.
About additional chance to receive a Critical Strike
I dont think it's correct to say that its effect is "additive with player's current chance to deal a critical strike". Attacker's chance to deal crit and defender's chance to receive crit - they are 2 different parameteers. Each of them has its own responsibility, its own caps, side effects, set of "flat", "increase/reduce" and "more/less" modifiers and so on. Their interaction is just that crit roll compares to sum of them. I think that phrase above need to be extended and clarified.
So, that's all. Hope someone will read, understand and transform it to good text.