The BS/WP is going to be better overall in PvP, due to the fact that defense is terrible in PvP. WP is just the better PvP secondary.
It shouldn't come as a surprise to you that you need help to kill. With the way i13 changed PvP, your ability to perform follow up damage got hurt pretty bad. Everyone was given resistance and your faster animating powers aren't hitting as hard as they used to. Getting the kill and getting out before you die is a lot harder than it was.
"the reason there are so many sarcastic pvpers is we already had a better version of pvp taken away from us to appease bad players. Back then we chuckled at how bad players came here and whined. If we knew that was the actual voice devs would listen to instead of informed, educated players we probably would have been bigger dicks back then." -ConFlict
Okay, I respecd, and in sirens i have all reflex powers but Elude, and let me tell you, it is incredible, u hit and run, if u and a partner dont finish the kill, slice with divine avalanche, and ur untouchable, u can pretty much As a target in Rain of fire with 40% aoe defence. I love the build, funny how i loved it yesterday but hated the death rate. So Much Fun. Thanks for your tip on this but i think this is my perma stalk 
. Went up 50 rep today and got an io so im pleased .
My /nin stalker still > most WP stalkers.
WP i personally tink is bad.
But, in terms of reality. It prolly goes like this now.
Nin->WP->Regen->Elec/SR
Personally, I prefer ninjitsu SOO much more then any other secondary for the decent defense AND the heal. Blinding powder is a rediculously under-estimated power as well.
-Epsilon.
I just rolled a Nin/SR Stalker for PVE.
Oh wait PvE is not allowed on the Stalker boards.
-placate-
I pvp...Alot... I know im not the best because I roll crappy builds. When AE was in its prime(in terms of exp, before the nerfs) i got a NIN/SR stalker to level 38 in one day. Since then have only played it in PvP. It is now level 42. This may seem sad to you, as it does to me, but i can only kill when grouped up with at least one other player. Once I strike with AS, and my hide is broken, I am immediately killed by blasters due to the level of suckage in /SR. I was wondering if someone could post a sample build for me that they use in pvp (MAINLY SIRENS), it would help alot.
Also, I recently rolled a BS/WP stalker which is now level 15. Should i level that one and pvp with it instead of the NIN/SR, or get my NIN/SR to 50. Take into account that Dbl exp weekend is in a week, and IMO both builds have the same gameplay, so its not really opinion based, i find them the same in pve. (just recently hit 100 rep after long time).
To go off topic.... why would someone take claws on a brute... seems a little weak to me(compared to builds such as SS, stone and elec.