The quick play units page in the post above has been updated. Everything has been as faithfully converted as possible, and some of the newer special rules have been included where they make sense. It is interesting to see how the unit costs changed (or where they didn't).
Here is the visualization for determining roll probabilities that I have been using.
Note: Cut all of these values in half if the defender has the Armored special rule.
Some things which can be gleaned from this; The lines are not parallel, higher qualities are increasingly more likely to succeed in attacks against subsequent lower qualities. 2+ is very hard to hit, even for other 2+'s. I believe this is one of the reasons AP exists in other games. Here, the only answers are Deadly, or just throwing more dice into the attack through things like Group Units or Powerful. Only 2+ (against 5+ and 6+) and 3+ (against just 6+) are more likely to succeed in an attack than not. 6+ success rate is closest to being nearly flat, so try using them to Charge stunned models when possible, or to fulfill shooting-only roles. I would avoid Charging 6+ units into melee unless they have special abilities which raise the certainty that you will Stun the opponent (so they cannot strike back with their better, more likely to succeed, quality). 4+ serves as a truly good average, as it is the first Quality in the scale which is less than 50% likely to be hit by all other Qualities.
Warstuff uses a completely cascading-roll system, each special rule which calls for an additional roll check further slices up already tiny probabilities. We should seek to limit stacking cascading rolls as much as possible (maybe to 3 maximum), this is why Armored already does not stack with Cover terrain. I am on the fence about whether Small should also not stack with covering terrain. Here is the probability of hitting a Small unit behind cover terrain expressed in formula: (attacker's success rate)*(attacker's success rate)*(.66)*(defender's failure rate) Looking for thoughts on this.