Void Reaver, after 2.4, is apparently, "wrecking fools," according to Korin on the Silver Hand. We all called him Loot Reaver before 2.4 -- if your guild could finish off Karazhan, and survive VR's trash, he was basically a pushover. But a whole combination of factors, including addon problems (with DeadlyBossMods and VoidReaverAlarm) that killed the addons that made it cake, as well as a few bugs and other problems with the fight after the patch, means Loot Reaver is getting his revenge. He's back to being a real challenge in Tempest Keep.
The hardest part of the encounter is avoiding these orbs he shoots out at random spots where a guild member is standing. When he shoots one out, everyone in the guild has to move away from that spot and each other, since getting hit with one is instant death. Those addons were meant to tell you when an orb had been fired, as well as let you keep an eye on the proximity of where it was hitting (so you could easily dodge it). But without the addons, people are back to judging where the orbs might land, and guilds that haven't practiced the fight much aren't that great at judging. Not to mention that there are some bugs, apparently -- some of the orbs are invisible, and others may even be moving through walls and underground.
The fight is still doable, but apparently Blizzard wasn't happy with how easy it was to waltz in there with some addons and collect your loot. Whether it's bugs or addon changes, Void Reaver is currently back to "wrecking fools."