I run Festering Claw, Its super useful on down time that the abom gives me a Fest Wound, but i also run UF and have legendary bracers so I dont know depends on gear and personal choice, it doesnt sim my dps by too much lower either a few hundred , so its not a complete loss
Well first of all depending on the fights tier 1 talents should be changed depending on if it has cleave or plain old single target.
All Will Serve does a %!&# ton of damage over the course of a single target fight (look at logs).
- Nylthendra/Ursoc/Dragons/Elerethe
Although I may get some flack from people who go bursting sores on Elereth for the 4 spiders x2 that come out during the first phase. Which really seems more like padding during the first phase of the fight- DND/SS spam is fine. AWS will be better for the full duration of the fight(look at logs).
Bursting Sores is better to be talented on the add fights.
- Il'gynoth/Cenarius/Xavius
With that being said. I have very similar stats as you do and have run Simulations on my stat weights for different fight types. I found that where I'm at right now haste is actually weighted slightly more heavily than crit single target. I couldn't tell you at which crit benchmark haste overtook it probably somewhere around 31%/32%. My haste is 5% higher than yours though so I would assume +haste/-mastery would help you out a ton. You would have to run sims on your own stat weights for specifics.
However for fights with heavy adds sims showed me that- believe it or not mastery was weighted VERY heavily(which makes sense, our cleave is shadow damage). I can't see this helping in any EN fights but something to think about in the future.
As for Tier 6 talents I am a little torn myself. SimC tells me Necrosis is slightly better single target, but in execution I get much better numbers using SI. Also looking at various mythic kills I see UH dks using SI themselves. Take a look at Methods Mythic Ursoc video and the DK is using SI. I myself will be using SI until I get solid evidence that necrosis is actually a better talent in execution.
Get SimC and sim after gear upgrades to get a better idea when your stat weights change = )
Got a little off track, and might be more than you were looking for but there ya go!