Yeh any unrelated addons should certainly be turned off in 25 man raiding.
Carbonite and Gearscore are well known for sending and requesting vast amounts of data that's simply not useful while raiding. This includes data transfer with fellow raid members.
Thats right, someone else using an addon can cause YOU lag.
There was a post on this topic waaaaay back in patch 3.2 on our old forums.
You can track how much you are spamming people with your addons and how much they are spamming you by getting Addon Spam
If you see an addon is sending or requesting vast amounts of data and you dont need it to raid - turn it off during raids.
The same goes for memory usage. If it uses lots of memory and you dont need it to raid, turn it off while raiding.