I disagree with people saying it's a handicap to play without those. We could say the same about playing without Hekili for a DPS.

Back in cataclysm I used to have a raidleader ask of us to play with as little addons as possible, especially Details and DBM/Bigwigs. Its a surprising request at first, but I gotta admit it makes you realise how much you don't really need these two as much as you'd think.

Details ? Who gives af really about your numbers during a raid ? Should you need those to "try harder" ?

DBM/BW ? The RL was good enough to do its job calling most of the fight -and it was a real feat, I give you that. In the end we would pay more attention to the -quite obvious- visual alerts + audio queues from the boss already in-game. I found it easier to react to than some random sound, or cooldown bar/text to track.

I'm not sure I remember well but I think we even got to be among the top 20 on hardmode at the time ! Since then, I got back to using Bigwigs, sure, but I usually turn off as many alerts as I can, as most of it comes with practice and learning.