I saw Verh use the term "soft Crit cap" somwhere on the forums. I knew about simple "Crit cap" but I don't get what the soft part means. I've only seen that used with Hit cap.
When talking about stat "caps" there are two types of cap, "hard" and "soft". Hard cap refers to a point at which increasing the stat further provides no benefit whatsoever. For example, once your chance to miss is reduced to zero for all your spells/attacks, increasing your hit rating will no longer do anything.
In contrast, a soft cap represents a situation where raising the stat in question still does give
some bonus, but beyond the "soft cap" that bonus is reduced in some way that makes the stat considerably less valuable and no longer worth stacking.
(Sorry if you already knew all that but I figured it was worth explaining.)
I'm not sure what context Verh used it in (and I'd imagine he could give you a more specific explanation), but with regard to crit, my best guess would be that a soft cap would probably come into play at a point where a class either frequently has some kind of buff to critical strike (
Shatter, for example), or uses abilities which have some innate crit chance increase (
Holy Shock,
Ferocious Bite,
Bloodthist, etc).
In these situations crit could be "soft-capped' if, say, a mage was crit-capped against frozen targets (but not against non-frozen ones) or if a warrior were crit-capped for Bloodthirst but not for his/her other attacks. Crit is still beneficial, but not as much as it was before the soft cap.
Hope that helps.