BRD rotation

[Viridiana]

I was wondering if anyone can give me a few tips regarding a decent rotation.

I'm currently using SS - VEN - WB - HS and rotate while hitting blood letter when available

You've got the right basic idea. SS buff is most important, followed by the dots, then HS. HS loses to Straighter Shot procs, of course. One thing to note is that most people do WB->VB, because WB is the higher potency of the two (except in some fringe cases).

Is it better to stack/stagger buffs or use them one at a time? Every time my DoTs need to be refreshed, I pop a cooldown. I've read some rotation guides saying it's better to stagger them - like Internal Release --> Windbite --> Hawk's Eye --> Venomous Bite --> Raging Strikes --> etc. but I don't understand why that's better.

Stacking them is going to lead to more damage overall. Note though, that sometimes you'll want to spread them out to make certain mechanics easier to deal with. A high-end example would be Conflags, where you pretty much have to split them to meet the dps check. Conversely, I tend to save mine in GX for sister phases to burn one down ASAP. Basically, it depends on the needs of the encounter, but stacking is more beneficial.

Also, if you're popping more than one at a time, start with the longer duration one. For example, RS->B4B->HE->IR->Barrage. This allows maximum overlap. I'll point out, though, that the desire to maintain this order is why I usually put my buffs off until the second set of dots come around, but that's largely personal preference. I find it a little simpler this way, while acknowledging that it's probably a very slight dps loss.