So when comparing Mod sets there are a few things to take into consideration.
Firstly is the amount of crit damage a character will have in general. If a character will have 200 crit damage before the Crit damage set bonus, a crit damage set will may only barely outperform an offense set since 230 crit damage is a 15% damage increase over 200% crit damage. Since crit damage is dependent on crit, a good rule of thumb is to go with offense over crit damage when you will be hitting that 200% crit damage baseline. Anything over 200% means that the crit damage set may not ever produce more damage than the offense set. It likely will, but it won't be much and will require very high crit chance to be better.
This means that the characters that ended up with over 200% crit damage after triangle and relics are very likely to get more damage out of an offense set than a crit damage set.
So that's the first thing a crit damage set isn't a 30% increase in overall damage. the actual increase must be determined by taking the crit damage number including all uniques, buffs, leader abilities and other mods + the set and divide it by that complete crit damage number not including the set. Doing so gives us the % of increase we will see to our in match damage.
For instance 230/200=1.15 Hence why I know that at 200 crit damage a set will only represent a 15% increase in damage.
Now the other part of comparing offense to crit damage is trickier, but actually not that tricky at g13 or relics compared to being at g12+5. This is basically determining what percent of your total offense 15% of your unmodded offense is. This gives you your actual damage increase for offense. That's right offense set doesn't actually increase your damage by 15% just like crit damage doesn't increase your damage by 30%. With incomplete gear levels we have to subtract offense from currently equipped gear before calculating %increases from mods. Difficult. Let's just pretend we're all g13 or higher.
So take your unmodded damage stat (physical/special, whichever matters to your character. Do both if your character uses both, but with 2 separate calculations not added together) and figure out what 15% of that is . Then divide that number by what your total offense is. This will tell you what your actual damage increase for offense is.
Now for the fun part. we take our %damage increase from the Crit damage set and divide it by our % damage increase from the offense set, and this give us the amount of crit chance we would need to have to make the crit damage set outperform the offense set. If the answer is over 1 then the crit damage set will never outperform the offense set.
Combining all this together gives us the handy dandy formula:
((Complete crit damage bonus including buffs, uniques, leaders, mods and relics +set)/(Complete crit damage bonus including buffs, uniques, leaders, mods and relics but no set))/((unmodded offense * .15)/(all offense including mods (with no set)
Or for those who don't like words in their formulas
C=Complete crit damage bonus including buffs, uniques, leaders, mods and relics
CD=Complete crit damage bonus including buffs, uniques, leaders, mods and relics including set
U=unmodded offense
O=modded offense amount not counting set bonus
CC= Breakpoint where CD set equals offense set above it CD is better, below it O is better
((CD/C)/(U*.15)/(O)=CC
