My apologies, I messed up some multipliers (put 6 ticks on marlows cremation instead of 8, 5 ticks on Grip/Hand instead of 6) and didn't add in some DD changes on my spreadsheet, so after killing a few alligators in remnants and getting all the correct numbers my necro is getting, here is the new list.
Also appears the skele's in remnant's undead city are pretty resistant to poison which would explain why it appeared earlier to me that Caress of Sivyana was a bit low, that or client bugged and wasn't registering my poison mod.
Moving forward, why is funeral pyre only 6 ticks and not 8 like the rest of the line?
Also I was trying to justify some changes to the Hand/Spirit relics to be better than casting Grip, since Grip is pretty much an instant DPS increase (casting 2 DoTs which allows you to add another in the line before they fade) and saves a spell slot. The only way I saw to do this was either drastically lower the mana for Hand/Spirit, add in some sort of DD to them, or both in order to make casting the single spells better on mana.
As far as some of the other considerations Remy mentioned,
Cast time - For me it's about efficiency here, as once I get DoTs rolling, I cast them all in the same order to maximize damage/duration. For full burn, casting 1 DoT a tick is the goal as to stagger out the durations, which for me amounts to less than a 4 sec cast time. Scitterpox is fine here because the next DoT I would cast is Marlow's for an 8 tick duration, so Scitterpox finishing 1 tick or same as Marlow's is fine.
DoT Duration - All the top 5 DoT's I would cast all have different durations, which dictates my cast order when I'm full burn. In XP groups however I normally only cast 1-2 DoTs before the mob is dead, so I stick to Claws and Grip. If the mob calls for more, I will toss in a Scitterpox or Marlow's depending on the amount of time I feel I have.
Damage / Cast Time - I feel this isn't that important for Necro's as you are still waiting on DoT's to finish. Overwriting DoT's before they finish just hurts your DPS/Mana. You are racing your first DoT cast.
Utility - Healing DoT's/Lifetaps are great. It allows me to tank a lot more stuff than without it, especially when they crit. Snare utility isn't as useful as the tiers climb, as I would rather DPS and tank than snare and run, as I feel it's faster XP. I also box with a druid, so tanking and DPS'ing is a better way to go unless I simply just can't tank it, but in most of those situations Snare wouldn't help me either.
Elemental Damage Scaling - I feel this is poor for Necro's if talking about elemental damage addition on gear. After some testing with my DoT's, +24-35 elemental damage (cold, poison, and magic were all tried) only resulted in around 1 DPS increase in damage over DoT ticks (+35 Magic got me 6 damage per tick on Hand, +25 Poison got me 4 for Caress, and +24 Cold got me 4 for Archaic). Also take into account we cast all elemental types, so focusing on just one is fruitless.
Scaling Options Avaliable from Gear - Our main focus, Affliction, is in small supply at the top end. Currently for my tier and what we've killed, the only two items I have are Mist-Touched Wardstone at tier 8 (which I can't verify anymore as we haven't killed Soul of the Keep since he changed from 18 to 6-man) and the newly added Hrugtah Hide Bracer at tier 10. The next option for necro's at my tier is the shoulders from Saitha. So from Tier 8? to tier 11ish, I have two to three options for Affliction 8 compared to six for Damage Inc 8 in the tier 10-11 range. Now to help maximize damage and increase scaling, I also need all five elemental foci on top of a decent damage increment, on top of conjuration and alteration mods, which becomes quite the gear juggle.
Spell Slots - I always have at least 5 DoTs up, Claws, Marlow's, Caress, Scitter, and Grip. Prior to just getting Grip a few weeks ago, I would keep up both Hand and Spirit in spots 5 and 6. Now that I have a spare slot, this is usually my floating utility (mez/pbaoe/another dot). Slot 7 is utility and in my case, target FD, and slot 8 is Ancient Lifetap. I don't feel this is any different than Mages/Wizards however as they have their own juggling of preferred spells.