Shield Break lowers mobs Evasion... The reason a WAR would use it is to help with the parties Accuracy. If your parties accuracy is fine theres no reason to use it!
There are times, god forbid you need it or not, That giving your entire party an accuracy boost might be slightly better than epeening damage.
what with this not being a perfect world, there are gimps, and not every party has a dancer, and in some situations people might prefer playing with gimp people instead of soloing.
Parties below ~50 are the most prime example, almost every player in that range is leveling a sub job (rather it be for 99 cap or just for 75/80), and don't gear themselves in the best manner.
I never said it should be used in every situation ever in the history of ever, i simply said, there are some situations where it might be, MIGHT BE, Slightly more beneficial.
lol o.o! your war is 37 and youre telling people to shield break? :P feel sorry for the parties you were gimping trying to level sub. and again when you take it to 40