In 25 mans, the other tanks are all in a different area of the room tanking their own mobs. Unless you want the Warrior to thunderclap for you during the 1/2 second that you're close enough together while you trade mobs in the Four Horsemen, for example.
Its use in 5 mans is obvious. In 10 mans, the tank situation is similar to 25 mans, the other will often be off tanking their own mobs -- but enemies hit for a lot less so the speed reduction isn't as major.
Not to mention, Judgements of the Just is the cheapest and most desirable of the slow-effects to have on single mobs if everyone is together anyway.. It basically only costs you a Global Cooldown for a spell that you cast all the time in standard rotation anyway.
Edited, Dec 9th 2008 3:06am by Losie