I think it's fair to say that the 'real' versions of fights aren't just a bit different, they're orders of magnitude different. Most of the coolest mechanics in any fight aren't just 'trivialized' for LFR but are completely gutted because they simply wouldn't work at all. Ever.
For instance, a fight that was STILL a monster on LFR early on was Durumu, and on LFR the color beam phase of that fight is quite literally just 'move the 3 beams to the 3 adds'. The only similarity to normal or heroic is that there are 3 beams of different colors.
On Heroic the mechanic was that you had the 3 colors, yellow moves on its own, blue and red would move with the person they were targetting. Blue you wanted to avoid hitting the blue add and you wnated to keep still, if you expose the blue add you might as well wipe (It does intense AE damage to everyone. The yellow beam would circle either counter or clockwise and eventually WILL hit the yellow add, which you then need to kill instantly if it happens. You minimize these chances by placing the yellow beam on the opposite side of the room from the yellow add if possible (There are actually 2 yellow adds on heroic but they always spawn 'near' each other so you would make a Y shape to maximize the average travel time). This one isn't a wipe unless you fail to kill it, but it does do extra raid damage so you want to avoid it. Meanwhile, the phase actually ENDS when the red beam has passed over 3 red adds and you kill all 3. The red beam needs to move quickly to sweep for adds, and stop when it exposes one (Pulling the beam off before the add is dead will cause an explosion). There is a soft enrage on this phase because each beam does split damage to everyone in the beam, you split your raid into 3 groups, one for each color, and your red team needs to TRY and identify where the adds are before they spawn so they can quickly wipe them out. You also don't want to cross beams too often since you end up splitting more damage over more people and spreading more debuffs. The debuffs you get are color specific and last the entire fight, and stack. So if you're in Yellow, you take like 1% more yellow damage per stack for the rest of the fight. THIS aspect of the mechanic means that your groups of color soakers actually needs to rotate which color they're in per phase. The yellow group the first time becomes red the next time, blue the third, etc. Just to clarify, you 'see' where the adds are by a very brief burst of a dull explosion where they spawn. So, there's about a half second window for your group to see the color splashes and process where the 6 different adds are in the room and position appropriately.
Now, that mechanic? Isn't even close to the hardest mechanic on the fight (Though it can easily wipe you if you do it wrong), but the LFR version aside from having the colors might as well not even be the same thing. It's like that for ALMOST every mechanic on every boss. You're doing yourself a real disservice unless truly the only thing you enjoy about raiding is looking at the graphics for the bosses themselves.
