Some questions about affliction warlock

[Alyzyr]

Hi there.
So i've been learning affliction warlock after playing destro for a year and I got a few questions which I hope you can answer.
I'm 534ilvl and I know affliction warlock does lowish damage at low ilvls but I really like a spec which uses channeling(like spriest).

Firstly, If i start channeling Drain Soul before boss is at 20% will it automatically do 100% additional dmg and make my DoT's do additional damage when boss reaches 20% or I have to stop channeling it and start again ?

Secondly, how do I get the maximum out of affliction AoE ?
I read that I should use Seed of Corruption on 5+ targets and get DoT's up on many people as possible.
Should I keep refreshing every DoT on every target (presuming that there's no time to channel Malefic Grasp without UA or Corruption falling off from atleast one target) or just apply them and start channeling Malefic Grasp on one target and spread (buffed) DoTs every once in a while with Soul Swap ?
What are your tricks or tips ?
Offtopic: For example as destro I used havoc on medium health target and Shadowburn on dying target three times which abled me to cast Shadowburn like 8-9 times in a row if the medium health target died soon after the first one. None other warlock that was with me in the same group seemed to do that in flex/lFR/tier 15 normals and I ended up with Shadowburn doing most dmg according to Skada/Recount while everyone else did most dmg with FnB Incinerate or Chaos Bolt.

Third question would be which spec benefits more from legendary meta gem - destro or affliction ?
I know that it has a chance to give 30% spell haste but how often does it proc ? Will it make a huge difference in my damage as Affliction?
Right now simcraft shows that I should do 166,5k dps as affliction and 178k as destro.
I'm one reset away from the gem so I'm rather interested.

and fourth question might be kind of odd. If I got only 1.x sec left on my trink proc and I can buff only one DoT that is about to fall off, should I buff Agony or UA ? Which is stronger DoT or higher priority to keep up on target ? They seem to do same dmg on all bosses. Always within 0,5% of eachother.

Also, I hope you can help me with my crappy gemming since I put it together with hurry 3 days ago and I didn't really have time to change it much.
I got haste and mastery gems mixed up in there because with mastery gems only I end up missing around 1-1,2k haste from 9778 breakpoint.

Bit info below:

Armory is here.

I got unenchanted wrist because I recently got it and also It shows that my tier 6 talent is Kil'jaeden's Culling even though I use Archimonde's Vengeance on most fights.

From simcraft if it helps with gem suggestion:

Scale factors:
int 4,82 haste 3,43 mastery 3,28

Thanks in advance if anyone actually bothers reading this wall of text and helps me.

EDIT: I also got ilvl 548 Shoulderpads of Dou Dou Chong but I use the ilvl 528 2pc shoulders because of extra haste it gives me and I'm told 2pc bonus is good on affliction.

[Kamswow]

1. I might be wrong on this but I think drain souls damage is calculated when you start casting it so you would need to cast under 20% for it to be buffed.

2. If the adds live for I'd say about 5 seconds after you have dotted them then just soul swap your dots on to everything. You can swap seed of corruption too so if you have all your dots plus a seed or two if you soulburned one then you can soul swap those around but it can be a lot of set up to get everything.

3. Affliction defiantly gets more from the meta gem. It is only a small increase for destro.

4. If you can cast a UA before your trinket falls just cast an Agony right after and they will both get the buff. Even with the nerfs I think Agony is still the best dot to get trinkets in to because it lasts so long.

Hope this helps!

[Turturin the Warlock]

1. I might be wrong on this but I think drain souls damage is calculated when you start casting it so you would need to cast under 20% for it to be buffed.

That's not correct. Drain soul's haste, intell, mastery, etc values are calulated on cast. The bonus damage from being in execute range will dynamically update as you cross the 20% threshold. This changed in MoP.

[Alyzyr]

alright thanks guys. I just got into a progression guild so I won't be playing affliction for a while because I don't want to hold my guild back.
gonna bookmark this thread though, gotta keep the the advice you gave me in mind.