The tons of icons and text is actually quite manageable - the amount of info you want on screen at any time is entirely up to the users particular GUI configuration. Practically every aspect of my UI has been changed. When leveling up and playing through the game early on the defaults are pretty much fine. A few things are useful, like the locate mod, where you can drop a dot onto your map/minimap based on a set of x,y coordinates.
The Leroy Jenkins video goes way back to well before the expansion. I'm doing 10 and 25 man raids now where we have to do just that, go over the strategy in detail as the boss fights can be complicated before each fight. Then go in and do it... but not leroy style picking up an entire room. The leroy video seems really hectic because it is - the dude wiped the entire raid - they all died. On a lot of bosses you can hardly have anyone go down - everyone needs to do the right thing or your screwed.
An example of one where you cant really lose anyone would be Netherspite (huge ghost dragon) in the 10-man raid Karazan. When you start the fight three portals appear, one on either side of a big room. These are red, green and blue. A beam comes out of each, that if it hits Netherspite either regens health (green), do more damage (blue) or take less damage (red).
So the team must intercept these beams. When intercepted, the player in the red beam will always be hit by netherspite, but the beam gives them a TON of health that slowly diminishes. Each of the other beams has a certain thing it does to the player in it that is both good and bad, so any given player can not stay in the beam during the entire phase. A rotation has to be set up with certain classes taking certain beams. When you step out of a beam for more then 7 seconds you get a debuff that prevents you picking up the beam for a certain number of seconds (a minute or so).
The portal phase lasts a certain time, then switched to another phase where the dragon stays in one place and does tons of damage so everyone has to run to one side of the room to escape... there much more to it but this is getting long. In the odd chance you're interested a complete strategy guide is here: http://www.bosskillers.com/cgi-bin/bbguild/index.cgi?action=view_guide&guide_id=37&sid=f47Sv4KLdX
My point is, to succeed in this fight, it can't be hectic. Everyone will just die really fast. Also if you don't get him down in a certain amount of time he becomes 'enraged' and pretty much destroys everyone no matter what you do.