I really like it on my Hydra support champs to help protect the squishy damage dealers a bit more.  Kantra and Tuhanarak are both in it for my NM team.  Tuha built fast with good survival and acc / res.  Kantra in a more damage based Guardian set.

Don't use it much for DT myself but I know it can be used there on someone like Vogoth for more protection.

I use one on Mithrala for my Nightmare Hydra team.

Use it on healers: Opardin, Doompriest. That's for clan boss, hydra, IG hard. Even if you don't make super good use of the ally protection, it's still basically a regen set (slightly weaker).