I im pretty sure that strafing let you most of the time also block/parry attacks coming from 'behind' when you went in a WIDE radius while kiting (or running from) your enemy. And following this thought the frontal angle would be somewhat around 160° ..

- winkel.png (10.82 KiB) Viewed 2100 times
Another thing to strenghten this statement was the ability to also cast spells while actually having targets behind you. I used to do this sh*t with my BW on live and pretty much could cast on targets i saw at the edge of the screen.

- Chizune_003.jpg (138.78 KiB) Viewed 2100 times
Thats how it looked about on live (obviously i cant recreate the original one).
Another thing to mention here is that the stuff about the angles was not bount to your running direction but the direction your camera was faced while moving with a held-down right mouse button (i hope its understandable what i mean). thats how these moves above were actually being possible.

- chizu-mod.jpg (150.15 KiB) Viewed 2100 times
thats about the stuff as i remember it