Would you be willing to share some of your tactics (positioning, setup, attack rotations, etc) ?

My quad DKs just turned 71 in meh gear, and I gave Nexus a try with a dedicated lv 75 paladin healer in fair gear. Everything went down well, except for the last boss that plays freeze tag with everyone. We got her to about 40k and bit the big one. We decided to try again when I can pump out a bit more dps and we understand the encounter better.

As for tactics, mine were pretty simple. I have one spec'd for tanking, the other three for dps, though all four put out about the same dps, and have the same basic spec. The tank is spec'd more for aoe to hold agro off the others and is slowly building up a tank gear set. Anti-magic shield is on 3/4 and on rotation. For the bosses there, it really didn't seem to help much, but for the trash it worked fairly well. Tank stays in frost aura, dps stays in blood aura. We try and keep ghouls at all times. I never gave thought about aoe damage on the ghouls taking the AM shield down instantly, just never noticed it.

It was the first instance I took them to. In normal every day leveling, I single-shot just about everything, so I don't get a lot of practice on useful tactics, and I pretty much only use Icy Touch, the next white damage hit, the ghouls take their hit, and if the target is 9k or under, it dies. If it is over 9k, I wait for the diseases to tick once or twice and it dies. Anything around 30k or under usually never makes it past my first runic dump.

In Nexus, I completely forgot to use the Horn for the strength boost (d'oh), but I doubt it would have turned the tide on Keristrasza. Bone shields are up all the time, to reduce the initial multi-mob burst damage on the tank and for the dps to buffer any lost agro and aoe (though in practice, agro was never lost).

I'm still working on learning how to bring the target in tight enough so that everyone has melee range as much to 100% as possible. Though I am close to having it where everyone gets their attack in, I'm certain I'm still losing some serious dps when they are outside melee range and their rotations get out of synch. My biggest problem is that the mob I am tanking likes to maintain a certain distance from me, and keeps backing up, focring me to reposition, which causes target to reposition, etc.

My basic sequence was intended to be IT, PS, BS, BS, SS, runic power dump, SS, SS, SS, runic power dump. In reality, it seems to work out more like IT, PS, BS, BS, SS, runic dump, BS, BS, IT, PS, SS, runic dump because I am too impatient to wait for the runes to regen for the triple SS, and see those blood runes just lit up ready to use. I have to take a closer look though because I feel I am missing something on the runes not being readily available for the triple SS. On multiple mobs, everyone does Pestilence and Blood Boil in place of the two BS. [I took a closer look and the reason is my spec, I need to spec into Reaping to allow the triple SS in the rotation].

I treated all the encounters as tank and spank, nothing special.

Telestra went down easy. I used the AM shields, but I'm not convinced it really did much good.

Anomalus went down easily also, just switching to Chaotic Rifts as they appeared, and using pestilence to spread disease from Anomalus to any mana wraiths that happened in before I nailed the Rifts. I also used AM shields here, and again I think they helped only minimally because the rifts and mana wraiths never lived long enough to cause any real issues.

Ormorok went down surprisingly easily, in stark contrast to my shaman team who has about a 50/50 chance on him (they are lv 72) and usually a win comes with only one left alive. Ormorok did the positioning tango thing I alluded to above, where I dance forward, he dances back, I dance forward, etc. This is annoying as hell because it causes my dps to floor because about 30% of the time my dps is out of melee shot for an attack or two and messes up the synchronized rotations. The irony though is that it kept all of the DKs out of the spikes every time, so though it took a lot longer to take him down, I took fairly minimal damage. Once he enraged though he overwhelmed the healer's ability to keep the tank up, and my tank died. Ghoul form sucks the big one because it tosses focus out the door. I have keyclone on hot-seat PiP, so I just let the ghoul be and swapped over, reset focus to my next in line, and resumed. A few seconds later, Omorok hit the floor. My shaman never had it this easy.

Keristrasza did not go as well. We tried it only once, and it was our first ever try on Keristrasza on any toons, so we were completely green and not studied up on this boss at all. This boss has like 290k hps, and we did manage to take it to 40k before we all died. I think we did just about everything wrong here. Healer stayed behind her, tank had dps glued to him at her front, we never jumped to remove the frost hit, though we did move so maybe that was fine. I'm not sure how my guys kept getting behind her, because from my point of view they were not, but I do know that my guys kept getting scattered and I kept having to gather them back. I think if we had known more about this boss, we would have taken her easily. We should have had tank out front, dps on side, healer on side or otherwise out of tail range. Again I used AM shield on rotation to buffer against the cold attacks but I don't think it hepled at all.

Silvermoon/US
Quad DK team : Dèèkaye (tank), Dèekaye (dps), Deekayè (dps), Deèkaye (dps)
Shaman 5-box: Kynix (also doubles as boxed healer with the quad-DKs), Kyñix, Kýnix, Kýñix, Kÿnix
Paladin Tank: Kythor