I just ran regular Halls of Lightning, followed by Heroics HoL. Regular was easymode now at 80, I tried previously at 79 and wiped a lot and couldn't down the last boss. With the tips above and mediocore gear (pally tank, mage, 3 ele shamans, everyone is in basically blues except for 1-2 pieces of titansteel) regular was a cakewalk, the last boss was definitely easier with the stack-up-and-heal strat.

Heroic was a different ballgame, did wipe a lot but did kill all the bosses except the last. And as a challenge, I did two of the achievements - I killed the first boss with the buff (30% damage buff) and the second boss without getting the golems blown up. Basically the same strats as regular, just DPS hardcore.

The third boss is same as regular, I pulled him out to the previous room and put my guys in different corners. I did wipe 3-4 times on this, you need keys to individually heal people and hope for a bit of luck so as not to get one person concentrated for the lightning ball adds or the arcane blasts. There were no extras from regular, just everything hitting way harder.

I couldn't do Loken, would get him down to 40% reliably every time but he was hitting my team way, way too hard. I do think with a bit more gear (especially PVP gear) it will be doable. Loken is also apparently the #1 killer of players at the moment according to Blizzard stats, so I wouldn't be suprised to see a small nerf in heroic mode.

Anyways great tips, I do highly recommend not trying this instance until you are 80. I found it a ton easier to run at 80 than at 78-79. heroic is actually not too bad, you may want to just skip the 3d and 4th boss though until your group is decently geared up. The first and second boss aren't too bad, especially if you have a mostly shaman team (heals+bloodlust/heroism helps a lot).