Shodokan:

I dont belive this is correct. Last week i wanted to test hast out, so i reforged all item into hast, I used a trinket with 253 hast. had a total of 53% hast. I start hiting a target dummy and was expecting my runes to come off CD faster but no, they was still on 9 and 8 sec when i did 2 obli in a raw. I could not see any speed change in which the runes it self would come back from CD. but i did see that my runic power bar got full quite fast. You can test this out but i cant see that i noticed anything happening with the CD on the runes it self.

That said, thoes 3 sec in melee on a target will still be the same for both, only that the hast DK will get 1 more white, while the mastery will have its FS or HB hiting harder.

And rune gaining as DW is really not a problem, In arena (i solo play) i hardly ever get a free global CD in which i would need more runic power. Its more of the opposite where i get it full before i'm done with my obli, BS rotation.