User blog comment:LionsLight/Sunfire Cape/@comment-4073002-20120107204712/@comment-4073002-20120108122118

biggest problem I have with it though, is that HoG->Randuin's and then FH if you need more armor are much better items and removes the need for Sunfire's stats completety. The utility from them is much more valuable than the negligible Sunfire damage. The Randuin's slow probably ends up giving more damage too by giving the Kog or whatever that's actually itemizing for damage a chance to waddle up into range and hit for more than you ever could.

It's ok on a few champs like Rammus and Warwick, but it's not the greatest item in the game for every tank. In the occasion you need damage, there are generally better alternatives like Trinity, Abyssal Scepter, Atma's or something similar. When people do get Sunfire, the farming capability it gives is normally a large part of the reason too, not the teamfight damage.