But what I tried to say is:
Old = Modifiers * (Base + SP*(Base_Coefficient+(Crit_Chance / No_Of_Ticks)))
New = (Crit_Chance *.5 + Meta_Gem) * (Modifiers * (Base + SP*Base_Coefficient))
Math says more than a hundred words :P
Right now you have the crit chance added onto the base coefficient, at 3.1, if they behave like regular crits (which assuming from the wording they will), it will be multiplied instead of simply added, therefore taking into account % modifiers, and stuff like that.
If you have 30% crit right now, you get 30% more BASE dot damage (which while including your spellpower, doesn't include stuff like darkness, shadow weaving, malygos sparks, thaddius charges, etc.)
If you have 30% crit in 3.1, you get a 30% chance to do 50% (or 100% if they change shadow power accordingly) more damage - and that 50/100% extra damage DOES take into account stuff like malygos sparks, shadow weaving, darkness, etc.
Because the dot already benefits from such modifiers, but the pseudo-crit from shadowform does not.
Hope now it's clear what my message was supposed to mean