Balance-wise, plenty of earlier 2.x era level 50 content could use an item level cap. At i130 it's all a bit too steamrollable, and we're seeing that with people favoring the CT raids far above the later ones. The 4-man dungeon stuff that does have ilvl caps is just i110, which isn't much of a difference.

Considering the level 50 job quests now give you your i90 set of armor for free, I think CM and Prae in particular could have used a i90 cap at the very least to lessen the steamrolling. IMO it ought to be even lower to justify the fact they are 8-man duties, but it admittedly wouldn't make very much sense for the game to give you gear right at the same time as it puts you into duties that won't even let you make full use of said gear.