I must start by saying that you should give frost a try, since the buffs it received post 7.1 (even after the 10% str nerf) works in favor of the spec. Play style is different though.
If you want to ignore what I just said and stick to unholy, you could play TWD (The walking dead - DK + WW Monk + Hpal / MW), the basic idea is to focus a dps while death gripping the healer etc into the fist stun to increase pressure and hopefully get a kill. All the setups you mention (Dk/Ret, Dk/Rogue, Dk/Hunter) have different strategies and tactics. For DK/Ret, I would suggest playing Frost though.
You should know that there is not a single strategy which will enable you to win all games. Sometimes zerging a healer seems like the only choice because the enemy setup is kinda anti for your setup, and sometimes you might want to focus a dps to keep control of the game. So, create at least 2 different strats according to the enemy team's line-up.
You may say that the dmg output of all will serve is lesser than the bursting sores, but it gives you a ranged pet and resets the ghoul summon CD, which are quite useful is macro'd corretly. By the way, the All Will Serve talent had its prime before the nerf, b/c you could actually use Corpse Shield, get the damage reduction buff, and then dismiss your pet with macro. So your ghoul wouldn't die from damage and you could just resummon it. This is fixed though Take a look at this post for a laugh http://us.battle.net...pic/20747754694
The more wounds you apply the better, since Festering Strike (FS) takes away your runes. Castigator kinda compensates for that. But I understand the desire you have for using Clawing Shadows.
Just because you have Necrotic Strike doesn't mean that you should be using it all the time over your Scourge Strike. Necrotic Strike is best used to create pressure and opportunity to get the burst going. So, for example, you can burst your target during a CC on healer and towards the end of the CC you can start NS'ing to keep the pressure up. That is just one example though. Basically, try applying enough NS to keep the pressure going, then try bursting. Oh and you should use your big burst as >> Have 8 wounds up, then activate Soul Reaper, then cast Apocalypse.
Usually UH honor talents will be as (skipping the first 2 tiers where you take glad medallion etc): AMZ, Decomposing Aura for TWD (You might use Necrotic when you play with your Ret partner), Crypt Fever and Necrotic Strike.
UH talents may be selected (depends on your style) as : AWS, BRW, Castigator, Asphyxiate / Sludge Belcher (improved defensive for Corpse Shield and dmg etc), Corpse Shield (against meleecleaves) / Spell Eater (against spell cleaves), Infected Claws (again, this may save you from using FS, but for this tier I love Necrosis actually), Soul Reaper.
Basically, spamming Necrotics will never hurt that much, since you will be building up pressure, which will lead to a kill. Remember, you are applying necrotics which prevent the enemy healing, and your teammate is putting out damage. So damage is being prioritized over healing in that situation.
For ratings, I don't want to state the most fundamental things here, but you should coordinate / communicate with your partners. As previously mentioned, have at least 2 dominant strategies, one could be tunnelvisioning and one would be making a fast switch to healer via deathgrip. Let your teammates know about your CD's, when you have burst available, and when you don't have any defensives left.
Observe the enemy's Walling CD's, you don't want to waste your big burst when the enemy targets walls.
And most importantly, never ever give up. The fact that you are struggling at 1500-1600 does not mean you won't get higher, always try to improve yourself, think about what could have been better etc.
Before the arena game starts, adjust your talents according to the enemy team so that you get the maximum advantage.
Sorry for my long post, it may not be the best advice for you, maybe some other people will contribute as well, but these are my thoughts. Just keep playing no matter what and good luck !
Edited by Warmonger_Skulm, 05 November 2016 - 01:36 AM.