Thanks for the comments,

Yea the human racial does share a cooldown but indeed does free up a trinket slot.

I got my herbalism up to 75 (lifeblood rank 1) on all guys today. Also did some testing in WG all day with different specs.

I stuck to 1 tier as im only level 59 now.
Unholy is great at nuking fast but not enough survivability.
Frost is great when you get in a pinch, surrounded by horde pop hungering cold (round robin) and kill them 1 at a time.

Blood is what im sticking with for now. Will go deep blood (up to hearth strike) + frost at 80.
With blood (rune tap every 30 secs, potions, bandages, and lifebloom, improved blood presence) I'm able to effectively kill pretty much 8 - 10 people coming at me in a group.

The biggest problem I have is forst mages casting blizzard, though Ive learned to death grip + mind freeze + quick 2 second kill before they cast it. This will become even easier at 60 with strangulate.

DK's seem a bit overpowered in this bracket, we'll see how I'm doing once at 68 in the next bracket.