My brute is a Claws/Dark. I already don't find problems with endurance, so form of the soul would be a waste in my mind (see what I did there?), but the redraw is occasionally annoying.
Staff is a great pairing with dark, though. Build end reduction in the attacks and you can start using the other forms to good effect. And of course there's the defense bonus.
Where to now?
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Ah, wanted to update because previous post was a little unclear -- the end thing for my Staff/WP Brute was an issue only in the teens. Once you hit 20 you get Quick Recovery and endurance stops being an issue. But from levels 8-20 using Form of the Soul allowed my brute to run Mind over Body, Indomitable Will, Sprint, and (then at 16) Rise to the Challenge pretty much without any end issues whatsoever... and in other builds getting to 20 has always involved end crashes (because I'd get sucked into SMASH! and would stop paying attention to the end bar).
Once I hit 20--and especially once I hit 22, and could SO or IO Stamina and and QR--Form of the Soul became unnecessary for End recovery.
Just wanted to clear that up, since I can imagine a few of you scratching your heads and wondering "what is this guy doing that's making a WP Brute have end issues?" 
Scrapper Jack (SJ/WP Brute), Sky Commando (WP/SJ Tanker), Curveball (Rad/DP Defender), and a bunch more.
Oh hi Dechs! Thanks for your reply.
Claws is kind of a special case though. I didn't want to talk about it because the first rule of Claws Brute is "don't talk about Claws Brute."
*looks over his shoulder nervously*
So... uh... anyway, moving on. 
Scrapper Jack (SJ/WP Brute), Sky Commando (WP/SJ Tanker), Curveball (Rad/DP Defender), and a bunch more.
I can chime in on this. Staff/DA was my easiest run to 50 ever on a DA toon. I used the usual tricks- miracle and numi as soon as they became available, ToE proc in Dark Regen, early Atlas Medallion and PShifter proc... I think all that may have been a bit overkill. Even exemping down for Yin TF, my blue bar is pretty healthy, and thanks to the +def, I feel tanker tough at low levels.
edit to add: then again, I wasn't trying to run sprint in combat...
edit 2: I use Form of the Soul for exemping, but since I chose PP for APP, at 50 I'm using the +rech form. If you're curious about a somewhat pricey build, search my history for the build thread- I went with the 45/35/35 positional build and couldn't be happier.
... I've played Staff before and it's fun. I've played Dark Armor before and it's cool, but I find end management frustrating.
I hadn't really thought of combining them until I read a post somewhere about a Brute who did and relied on the Staff Mastery Form of the Soul toggle to keep the DA toggles in check. It was a comment made in passing, but it interested me a great deal... I just didn't follow up on it then (about a month and a half ago, if I remember correctly).
So I thought I'd follow up here. Has anyone had any experience with this? Exactly how big an end discount does Form of the Soul give at each level of perfection? I've never been able to figure that out. I've have noticed that my WP brute with staff had absolutely no problem managing five toggles and keeping a consistent attack chain going almost nonstop as soon as he was able to activate Form of the Soul... but Dark Armor is a liiiiiiiiiiiitle more end hungry, especially that glorious, glorious heal.
Anyway, I figure I'll try it out, but I was wondering if any Staff/DA brutes were willing to talk a little more specifically about how effective Form of the Soul is at DA end mitigation.
Anyone?
Scrapper Jack (SJ/WP Brute), Sky Commando (WP/SJ Tanker), Curveball (Rad/DP Defender), and a bunch more.