GW - Gloom
Scorp - Web Envelope
They are the key patron powers I would say for a NW. However, the whole thing leans on what you have already as NWs are epicly scalable even with their standard powers + pools, most have issues fitting patrons in.
I myself went for gloom on my lovely NW for the DoT, neg dmg type (so a 4th dmg type in his spec), improved ranged chain and for the -acc.
However, web is amazingly helpful if you lack range or vertical movement, plus inhibits runners. Perhaps posty some more info or collar me when on tonight mate @Starscreamer and can weigh it all up 
Blimey, you've got room for Patron powers? Mind posting up your build? I fear you might've missed something useful...
Cancelled in Three - MA ID #34608. Please play and comment! Top 10 placing in Projectionist's MA contest!
My NWs spec is not for public view - he's one of my "Great 3" - but I'll happily adivse and assist anyone anytime I can - collar me ingame @Starscreamer and I can maybe give ya some more pointers as well JamieB.
Oh and for reference - my NW has every possible delicious toy and trick he could have 
Don't listen to my good friend Star, he doesn't know anything about Night Widows honestly
I have a pimped NW thanks to Star
he helped me out on power choces etc, and slotting. Now after months playing the widow and 6 respecs later i'm happy with the build
I havn't got a patron in mine, i couldn't fit it in, and it lowered DPS.
Catch me online tonight if yor online @effy an i'll help you out
@Effy
Effy On Hot Sauce Fire/Cold Corr
Effy On Hot Chilli Fire/Dark Corr
Effy On Heat FM/SD Before FoTM
Effy Unleashed DP/EN Blaster 1st 50 @ Union
Can anyone suggest a good patron selection for a widow? i'm thinking two choices for each build.
Pvp build - single target high damage or debuff
Pve - Aoe, survivability (aid farming perhaps)
or should i perhaps ignore them and go for no patron and use what's available for widow?