grats on the completed heroics. my 2c on where your stuck..

Ahn'kahet: Elder Nadox, Prince Taldaram, Jedoga Shadowseeker down (haven't attempted Herald Volazj)
-easy with shams but with my mixed i start nuking with the lowest hp toon and last the tank.. still spamming my one-click macros of course with the hope the the others will auto-target and bash some one.

Azjol-Nerub: Krik'thir the Gatewatcher, Hadronox down (4 failed attempts so far on Anub'arak)
-i position my toons on the right side of anub.. all range that is prior to the fight. i move them far enough from each other so they don't get double-dipped when impaled but close enough so when i aoe the little trash bugs after anub burrows, i get them all regardless of which toon aggroed. my range toons never move (except for the effect of impale).

Gundrak: Slad'ran down (stuck at Drakkari Colossus)
i park all my range up against the little rails to the left (protects against the surge attack), as soon as you walk into the room prior to drakkari (who's on your right side at this point). i position them much like in anub. I basically just go to town waiting for the elemental. Then i taunt and start my hots/heals on whoever's on the pool, never moving my range.

Halls of Lightning: General Bjarngrim, Vokhan down (stuck on Ionar)
i split my range forming a big square in the landing prior to Ionar's steps. this prevents static overload jumps. heal whoever gets overload and lightning.. when he splits.. i just hot/heals on everybody.

Halls of Stone: Maiden of Grief, Krystallus down (stuck on The Tribunal of Ages - Brann just isn't healthy enough!)
gave me grief for a while as well until i got my healer a bit geared. i especially pay attention to dark matter and searing gaze and prepare for heal spam. dk has been a pain as a tank. pally's easy mode. warrior's in between. druid (soon).

Oculus: Drakos, Varos, Urom down (Stuck at Ley=Guardian Eregos)
i've attempted all amber, mixed green amber, mixed red green and they have been all inconsistent per my experience. when i did all ruby.. never looked back. i have done both parking the healer at the bottom of a ledge and the rubies above AND all on rubies without much problems. though there were times when my evasion was off that i had to soak some dmg. was helpful to have a standby healer down below for emergencies. if you'll have a healer below, be sure to maximize your distance so your healer doesn't get gibbed with orbs after planar shift.

Nexus: Commander Kolurg, Ormorok the Tree-Shaper, Anomalus down (can't seem to get past Telestra)
i park my range by the entrance and pop hero right away. soon as she splits i focus fire on frost, then arcane, finally fire. when she reappears, i mostly just top off everyone and zerg away upon landing.

Violet Hold: Erekem, Zuramat, Xevozz, Ichoron, Moragg, Lavanthor done (Stuck on Cyanigosa)
my toons are spread out on her side, far enough so blizzard doesn't catch 'em all. soon as we get pulled, i hit my formation hotkey to spread out again, and walk her away with tank and repeat dps. spam heal on blizzard' toon.

hope these help a bit. not an expert but very willing to share.