Truth b told, I thought the same thing, but Overhead SLash is vastly different from plasma brand which actually does more damage on the DoT side.
If you want PvP as a priority, DoT is not prevalent but in a PvE/raiding environment, it's simply better.
The thing is, both overhead and plasma can reset master strike with a full vigilance spec, and they don't share CDs which is a big plus. Again, PvE build.
If you want PvP, it'd be good to go 7/32/2. For PvE, 2/36 /3 seems better.
On a seperate note; we all began obsessing like hyper-efficiency freaks again. This IS NOT a good thing imho.... Next we will be discussing a rotation that has to include all the 15+ skills of GRD class( Which is INSANE.)
Maybe it's best to just say "Play like you want, choose what you feel is best."
I'm like jolee bindo in this, I'm big on letting people figure things out for themselves.