The defensive stats suck but you're basically paying 800g for 35 damage, which last I checked was pretty good when you'd otherwise be paying e.g. 1650g for 45 AD or 1600g for 80 AP. As a minor offensive boost to otherwise tanky builds, where you don't have a bunch of other offensive stats to multiply the value of getting AD or AP, that's a bargain even before considering that it's also AoE.
Sunfire is still a bad item because it automatically aggros stuff when you don't want it to. Jungle creeps aren't a big deal, though they can block some champions' skillshots, but not being able to hit a turret or clear Baron wards is pretty annoying. --- "Pokey and the man."
Also the damage mid game is actually really high. As a first/second item it is really noticeable how much damage it contributes. People don't first item MR that often and if they are you were winning the lane anyways.
Randuin's/FH are better in most situations but for some champs Sunfire is fine.
it should never be getting built as a first/second item on anyone though. sunfire + any other item is going to be inferior to warmogs/GA/Randuins/FH etc.
and its not that having it is going to hurt your champ or be completely useless, but the reason it is so useless is because it is NEVER the best choice
You argue with gcube? GET OUT OF HERE! --- <("<) <(' ')> (>")> <(' ')> <("<) <(' ')> (>")> <(' ')>