Weighing up the issues...

Here's a few ideas

ditch the e.13 DRS for a Blackspire Stinger and Gamut bashguard. It's not only a ton lighter but it works much better. I find the DRS gets constantly clogged up with mud and the roller/bearing needs replacing often.

Diabolous crankset is likely heavier than you need. Have a look at the new Shimano SLX, or if you can find a set of last years Hones

Wellgo MG-1 pedals. Likely the lightest, good flat pedal out there. The Straitline stuff is gucci but expensive and heavy. Same goes for the stem although I haven't seen a weight on the new one yet. Sunline AM stems are light, strong and relatively inexpensive.

Tires…that a personal choice I guess. If you're going to stay 2-ply definitely check out tubeless. I've been running 1-ply Maxxis Minion DHF's tubeless for a bit, but I'm still a bit wary. I tried tubeless with a Syncros DS-28 and didn't have success. I see the 32 uses that beadlock technology too, so I'm not sure how well they can be converted. I've seen others using them tubeless with good results, so maybe I was doing it wrong.

Look around for deals on a SRAM 990 11-34 cassette. The aluminum spiders will be nice to your Pro II hubs and they save you a bit of weight. The 34 tooth ring will get you up any climb no matter how much your bike weighs. Not fast mind you, but you'll still be pedalling.

That being said, I would have been suprised to see the original build hit 40lbs.

…I noticed when I calculated the weight with single ply tyres and tubeless I was able to lose a fair amount. I currently run 2-ply tyres and love them because they feel so solid and I have yet to puncture (before I punctured regularly). Does going tubeless mean I can get away with single ply or are they still likely to fold under speed in corners etc?

Tubeless can be run successfully on either DH, wire-beaded or folding casing tires. I generally run 2.5 wire Nevegals on the back and same size/type Blue Grooves on the front but have been running the folding bead Nevegals on the back of my big bike since January last year. I had 1 flat in 10 months with many, many Whistler days thrown in there. The only flat was on my last day, last run at Whistler (bend the rim inward so the sealant could not seal around the bulging bead…..wire bead may have helped in this case). The one concession you must make when running the lighter casings as tubeless is that you will have to run with a little more pressure. I generally run between 20 and 25 pounds with the wire casings and between 25 and 30 on the folding bead casings. No squirming, excellent feel to the ride, no flats and mega weight loss (about a pound difference per tire just for the rubber without factoring in the rest of the tubeless conversion).

Given that I ride with the finesse of a dump truck, I can really give my endorsement to this without any hesitation.

Also consider RF Atlas for the cranks/stem/bar. Light and tough…

Another vote for tubeless, although I have had two issues with the kevlar nevegals, but none with the tubeless wire bead. I'm not sure if they make a
kevlar bead tubeless version, but I'd try that if they do.

Headset: Crank Bros Iodine
Stem: Sunline AM
Brakes: I'd evaluate what you need here. For your weight, and the bike's intended usage, I think some Elixirs would be more than acceptable.
Front Der: simply XT
Rear Der. Stick with Sram X9
Cassette: A Sram PG-990 or a XT would be nice
Chain: Try the KMC XSL chains
Chainguide: DaveM has the goods there
Pedals: Again…DaveM.
Rims: Opt for some pricier, more reliable Mavic offerings. The 721s would be a good choice.
Tires: Given the usage, I'd go for some Minion tubeless tires.
Saddle: this is a personal preference, so go for comfort before weight. The WTB Devo/Deva saddles are lightweight (in the Titanium versions) and comfortable.

is it ok to mix SRAM and Shimano?

Front Der: simply XT
Rear Der. Stick with Sram X9
Cassette: A Sram PG-990 or a XT would be nice

Also a question on tires, if I decide to go tubeless with non-specific tubeless rims, does it matter if I get UST tires or not? Seems a stupid question to me but just want it cleared up since I have no experience with tubeless.

What about shifters? Does the Gamut bash come in the clear colour by itself? I can't find it in anything but black when sold on its own. Also what do people think about FSA Gravity light crankset?

is it ok to mix SRAM and Shimano? Also a question on tires, if I decide to go tubeless with non-specific tubeless rims, does it matter if I get UST tires or not? Seems a stupid question to me but just want it cleared up since I have no experience with tubeless.

What about shifters? Does the Gamut bash come in the clear colour by itself? I can't find it in anything but black when sold on its own. Also what do people think about FSA Gravity light crankset?

i think Gamut only comes in colors…no clear.black,blue,red and white.
http://www.universalcycles.com/shopping/index.php?category=58

it's ok to mix shimano/sram on the front derailuer but not the rear.

if your gonna go with shimano stuff and your gonna order on-line. the uk is tuff to beat for pricing. (eg slx crankset $135 canadian)

i think Gamut only comes in colors…no clear.black,blue,red and white.
http://www.universalcycles.com/shopping/index.php?category=58

it's ok to mix shimano/sram on the front derailuer but not the rear.

if your gonna go with shimano stuff and your gonna order on-line. the uk is tuff to beat for pricing. (eg slx crankset $135 canadian)

cheers for clearing that up mate, BTW im from the UK! Not everything is cheaper though.

it's amazing as to how much cheaper shimano stuff is there, compared to here(N.A.) ….and what is up with maxxis tires??the reg. durometer stuff is dirt cheap(less then $40) half the price as here,yet 3C tires are same($75)?

i wonder what the new Hope Tech brake line-up will be like?new lever looks good.