Glancing can be a couple things. I think, though not 100% sure but if damage is too low you will glance, I think sometimes like a scimitar vs highest armor and you will seem to glance more often, but really I think in native the only time you will glance is when you trigger the sweet spot.
Sweet spots have 2 phases, the first does nothing, the second interrupts with minimum damage. This all seems based on the amount of time that has passed since you released a swing, not quite exactly where you hit in the swing per say. This is why a thrust that misses then is turned back into you will do damage at point blank range, or why you can thrust straight down at point blank range and hit someone's feet (impractical in a regular fight).
I think if you have a lot of lag people might not be in quite the place you think they are, resulting in a glance. Sometimes people also move into your swing, especially now since there is a lot more facehugging/swinging round each other now a days, you are likely to have people run into your weapon early, causing the glance.
I don't really see an excessive amount of glances or something appearing weird, most all my glances are from sweetspot early hits, but I tend to stick to US servers where i have 15 to - 60 ping.