Hi,
You guys already answered the OP quite nicely about the impact of +WS pre-2.0.
Regarding Glancing Blows, I just have a precision for the non-beta players (or even the beta ones that didn't pay attention when this was fixed) about how it was scripted on Nostalrius.
The mechanic is properly scripted (unless it was modified since I stopped playing on the server mid-2013). The only thing is the 310 cap was not chosen. Instead, a cap of 315 to fully nulllify the damage reduction from glancing blows was used.
I did my best during NR beta to report as many things as I could, and the Glancing Blows issue was one of them. I compiled as much information as I could regarding the glancing blows damage reduction formula to help the staff.
Long story short, the formula said to be "Athan's" formula regarding the GB damage reduction was deemed the more appropriate by the NR staff to be applied to the server, and it implied a +WS cap of 315.
Not only it seemed more 'logical' to have a 315 cap, it turned out the 310 cap was claimed everywhere to be the cap against a raid boss to have 0% reduction on GB, but actual tests without statistical bias to corroborate this number were nowhere to be found.
I'm not gonna detail Athan's formula, I don't remember it exactly and I'm sure it can be found somewhere online, but it came down to having still a 5% malus on glancing blows when attacking a raid boss with 310 WS, resulting in an average 2% reduction on white DPS.
Apparently, most people claimed 310 to be the cap because the 5% malus on glancing blows was quite hard to "feel" or record properly because of the damage ranges of the melee weapons. Only actual tests performed on thousands of glancing blows could allow that. And unlike other formulas claiming 310 to be the cap, Athan's was actually backed up by such tests.
Basically, the empirical tests regarding Athan's formula and its 315 cap were deemed more accurate, statistically unbiased and consistent by the staff.
Sorry for the long post, I just thought that you guys might find this worth knowing.
It's quite impossible to know exactly how Blizzard handled the GB reduction, at least not with a 100% accuracy, so the devs just chose the formula with the most coherent "background" and tests to their knowledge, i.e. taking into account that a 5% damage reduction was very hard to record without proper tests, making 99% of people agree about the 310 cap, whereas actual tests with a significant amount of GB were carried out to conclude that the cap was actually 315.
Of course, as always, if you think the staff was mistaken to implement this formula, if you find sources more trustworthy than the ones I (and they) found, you can just write a report and the staff will be thankful from your knowledgeable input and happy to change the formula to the exact 100% Blizz-like one I guess.
Have a nice day