But in all honesty, are these addons really necessary for raiding? There's some interesting arguments both ways.
One of the most convincing that I've heard is that if Blizzard really wanted you to use things like Omen, they would have built a threat meter into the game itself. That does make sense in a lot of ways. The rebuttal to this argument is that Blizzard provided a huge Addon API for programmers to make things like Omen.
Another argument that I've heard thrown around is that addons detract from the spirit of the game. This one actually rings true. After all, think about the role playing value of the game a bit. Say you're fighting something we've all done, like High King Maulgar. We all know that he whirlwinds about every 30 seconds. This isn't a big deal after you've learned the fight, because what ever boss mod you're using will pop up a countdown timer to the whirlwind, and then even give you some audio alert when he's about to spin around and kill all the melee.
If this were real, would you have any warning that Maulgar was about to spin around like a merry-go-round? Probably not much, if any. You sure wouldn't have a colorful countdown bar remind you. But then again, this is a game.
In my opinion, addons are a necessary component of any successful raider or end game player. They take a lot of the guess work out of the game, and let you have a better time playing it.
What do you think are the necessary addons for raiding? If you've ever killed a raid boss without addons, how did you do it?