If you're looking for Optimal:
Buy Pillars > Buy Kingly Upheaval. The 1200 bonus armor on Pillars plus the sta > nearly everything else make this the spot you go off-set at the 277 level, so it's really BiS, especially for a boss like Fester where the damage is almost all physical.
In best terms, 2pc bonus head/shoulders normally as you're gearing. Since you have the 264 gloves, either one would work. The general rule for the 2/4pc is:
At 251 Tier Head/Shoulders
At 264 Tier Head/Shoulders. 4pc At 264 for high burst damage fights (Fester is not burst damage unless you run heroic - Do you have a good Holy Pally? Makes the fight cake) or magic damage fights like LDW, Sind, and LK.
At 277 Tier head/Shoulders/Chest/Hands as they are BiS individually (or very, very near and bonuses push them over the top)
Basically you get more bang for your buck with Pillars as your non-set over the set legs than any other gear for any other slot over the set pieces, which makes Pillars/H Leggings of Lost Hope the set breaker (H leggings for magic damage fights).
Back, Chest, Belt are the three pieces you should get first if surviveability is a bigger concern than threat. Many would suggest Cloak > Belt > Chest (Cataclysmic first, then tier unless you have just loads of marks sitting around) because of the cost of the gear. I've always disagreed and suggest Cataclysmic, Vergis, Cloak, but that's my opinion, you'd be hard pressed going wrong in either direction (all 3 have bonus armor which makes them very attractive).
After those three, tier helm or shoulders (to make your 2 pc, assuming you replace the legs with Pillars), CSK, and then the other. And finally tier chest (so you can upgrade it, the 251 is pretty far behind the emblem 264).
Neverending Winter Exists... honestly. Our Holy Pally even has it.
Rings - Clut of Fort is good, but any stamina ring from ICC25 is better than your ToC ring. THat being said, the Heroic Valkerie ring and Ony ring are best in slot until you get the ICC25 armor ring from VDW if you can get your guild to run ToGC10 Valks and Ony25 because the armor on them > stamina on other rings.
Wrists - DBS10.251 wrists are better than the Morrowgar25.277 wrists for most fights, high magic you'd flip them.
Trinkets - If you have access to ToC/ToGC25, Scarab is great. Unidentified Organ from PP10 is great. Obviously Fang from Sindy25. CSK is purchasable. Mix and match appropriately (e.g. fester is dual armor).
Don't forget to put the +40 crit scope on your rifle for the extra TC crit.
I'd put BD on your wep rather than Accuracy - if you're worried about taunts landing (LDW, DBS, Fester, oozes, PP, VDW Adds, Sind) glyph taunt, then even as low as 160 hit you're good (maybe lower, that just seemed to be the magical number for me).
I run with glyphs of Dev, Taunt, and Shield Wall, though swapping Last Stand in and out with Taunt would work if you're a constant min-maxer.
The only enchant I'd suggest you change right away is your sheild. You have 567 defense, replace the +Def with +Sta on the shield.
Your glyphs are threat glyphs... are you running with guys pulling 8K+ in 10? Spec looks okay given what you said about Donovan (no druid to keep him rooted?). It just seems a little overkill to be glyphed for threat too unless the DPS is just going hog wild...
In which case I'd recommend grabbing the 1.5 wep speed axe from Gunship25 as a threat stick. The Heroic version actually has more EH than any non-LK drop. Don't let them argue with you on this one ;-)
As for surviability, it's really an armor game. In most fights in ICC armor is very, very valuable. Right now with no heroics and limited access in 25, I'm sitting at 34,750 armor, raid buffed to ~37k and during a third inhale on Fester it's over 40k with an indestructable pot. It really, really helps and makes you easier to heal. Of course I have become something of an armor hoe because I'm terrified of relying on healers, so armor makes it easier for even lesser healers to keep me topped off (of course the Holy Pally in our 10m critting for 100k is nice...)
Knowing what your 10's healing setup is like is probably the biggest key. 30k armor (36k with buffs and indestruct pot?) is more than enough for Fester with the 30% buff if the healers are switching quick.
You're chaining Last Stand and SW right? (I actually prefer to start with Last Stand because it has a longer duration, making it a little easier to manage.) It really shouldn't matter if you have big-ass heals coming in, but it will help. The other thing I've done to help with that fight is use SB as I taunt, to help a little as the healers switch over. It's usually up again for the 3rd inhale if you taunt right at 8 stacks.