The Rogues had now reached Act 4, where the monsters were plentiful and the waypoints few and far between. It was time to see what the Sorority Cheerleader Firing Squad™ could do in Hell!
Welcome reinforcements have arrived! 
That particular phrase was the greeting Hawkmoon tended to get upon arriving late to each session. And it looks like Hawk is needed! All of the rest of the Rogues owe her a debt of gratitude for tireless and unsung work with Prevent Monster Heal throwing axes. "Is that monster tagged yet?" was the second-most heard line over the TeamSpeak server. The most-heard phrase... well, we'll get to that a bit later.
Look - it's the Blue Man Group! Everyone in this photo is feeling blue; even Svava's stamina bar is blue from a shrine. Izual took a long time to kill, but was a lot less dangerous than some of the random bosses that the Rogues were running into. Lots of hit points, but no real threat.
Now this was a dangerous boss here. Cursed/Extra Fast is nothing to sneeze at, and it appears as though one Rogue is going to fetch a body off to the left. Kick in the high fire resistance on this demon, and it was a nice battle.
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This boss battle took forever, even longer than Izual. The boss is Fire Immune, which cuts out all damage from Enchant, and Stone Skin, which nullified virtually all physical damage. Then he was Magic Resistant to boot, cutting out almost all magical damage as well. The Rogues had to keep running through that town portal to the left for more arrows before this boss finally hit the floor. Thank goodness for Prevent Monster Heal!
What are the bats hanging from?! I'm sure many long-time Diablo players have seen this before, but it always amuses me. This is down in City of the Damned.
This is a combo that doesn't show up very often: Holy Freeze aura Hephasto. Despite this seemingly difficult situation, I don't think that Heph managed to kill any of the Rogues (thanks mostly to Knockback bows). This picture came out well, as it managed to catch all seven arrows (and Jaffa's crossbow bolt) in mid-flight.
The Rogues get a greeting at the entrance to the Chaos Sanctuary. There are a lot of Doom Knight bodies on the floor and more crowding the doorway to try and slice some Rogue meat. The boss pack at the entrance forced a retreat back down the River of Flame, but all foes were eventually wiped out. The fighting in the Chaos Sanctuary was difficult, but I don't have any pictures of the seal bosses. I must not have had an opportunity to take any.
Here's Big D himself, but there's actually a story behind what's going on. We were in the process of killing Diablo when ME0003 lost his connection and dropped out. You can see that MoonGrabber's portrait isn't up at the top of the screen with the other Rogues. As a result, we killed time for a couple minutes while waiting for ME0003 to reconnect. Big D continued to rampage around, but if you look at this picture, NONE of the Rogues are attacking him! 
I was losing all my respect for Diablo until he trapped Svava in a bone prison (which did not appear on my screen, I thought I was still running around normally) and proceeded to kill her. Lesson learned: don't trust what the screen tells you.
Another nice picture of Diablo; this looks like it's also from the period when we were waiting for Moongrabber's return. After ME0003 managed to get back into the game, the Rogues finished off Diablo easily. Sad, isn't it, that random boss monsters are frequently more dangerous than Diablo himself?
With Act 4 complete, it was time to wrap up Nightmare by going after Baal on Mount Arreat.
