Alright. It seems people are pretty mistaken about why people play a dh. "Oh, because of momentum" "oh because of spammy abilities." I play the dh because of its lore and the essence of attempting to keep a demon contained within. As such, i like the demonic side of the spec.
On beta, ive been playing the 2,3(or 2 when i have enough haste),(1 or 3) ,1,2,3,1. I like how it plays, and prefer trail of ruin over fel barrage, but since fel barrage is so op right now, i have to sorta feel pressured into it. As to dark Slash vs others... Dark Slash is a garbage playstyle and i will refuse to play it even if it is the "best talent." I prefer the blade dance/deaths dance while collecting souls that spawn like crazy. As to the dps, at this point, we know we will need numbers, but hell, we dont even have all the azurite talents listed yet. And since those talents are going game changing like tier sets and leggos... i am still holding hopes on what we will get.
But, as it is, i hate dark slash. Its the worst talent... even below nemesis in my opinion. I believe both nemesis and dark slash should be changed. The change I would do to nemesis is simply change to change it to a more fun spell. I always liked how in the leotheras fight, the demon would come out, and the two would attack you, so why not make it that? Make it an ability where it spawns a shadowy Meta form (or shadow form of you if you are in meta) as a "guardian" that attacks the target you attack, with the same exact attacks as you for x amount of seconds on x amount of cooldown, while being uncc-able. (only auto attacks if you are ccd). To me, this is already infinitely better than nemesis, and not to mention, it would no longer be on a single target, so if you need to, you would be able to switch targets. It would be both Single and Aoe friendly
As for dark slash, simply make it a new hard hitting ability that costs fury to use on X cd (lower than currently to like 8 seconds and based off haste) and transforms your next chaos strike into Annihilation. And in meta, it transforms to Void slash, a very hard hitting ability. Instead of increasing the next annihilation, it reduces its own cooldown by X seconds so you get like 2 in demonic) and the next demons bite is transformed into Demonic Slash which is as powerful as a chaos strike (normal) and gives you increased fury (40-60 a slash). If you had taken Demons blades, then the next few "procs" are called Dark Blades and are as powerful if you had spammed Demon's bite, and fury generation would be similar. Insatiable hunger, adds another 20 on top. This would change up the playstyle very differently, as they want to, but not in the sense of forcing you down only a certain path. This should allow the opening to either using first blood or this with any of the playstyles, while not dramatically changing the "secondaries" needed and becoming fairly inter changable. Full "single target" or "add killing?" take this. Cleave? First Blood. Like Meta a lil too much, cycle of hatred.
Though, I would change Cycle of Hatred to simply changing Metamorphosis having 2 uses, than one, while also giving it a usage cooldown of 1 min 30 seconds. So, use meta, hell, you even use demonic, so you get the extra 8 seconds before popping meta and after. (8 sec +38 sec meta) well, you still have to wait another ~50 seconds before you can use a second meta. If its too powerful then? simply have meta having a lower cd then to 2 mins. I dislike the refund system. Its too rng base on top of rng to having enough fury.
Momentum is fine, as it has it niche in pvp, as well as world pve, but its a garbage talent for raiding. I find it very fun, and loved it during Emerald Nightmare, but with the loss of bloodlet, it lost most of its true essence, and with how raids are becoming even more exaggerated on players not moving or using their movements to do certain things, momo has nose dived.
As to other talent changes... id actually make Demon Blades baseline, but not in its current form. Id make it Demons bite with a cd of X seconds that gives you instant 20-30 fury while also giving you the Demon's Blades talent as an undispellable buff for Y seconds (2 more seconds than the cd), while also buffing demons blades talent back to its original form (still without the ring). Insatiable hunger would remain the same, but not gets rid of the cd on demon's bite. And the talent to replace demon's blades would be chaos blades (different then current) where your chaos strike have a chance to singe your blades with chaos energies and increases the fury generation of the Demon Blades buff and gives your next demon's bite 5-10 more fury. Compensate Insatiable and Immo if need be.