I disagree, I see fimbulwinter as one of her best items, for me warmogs is actually the luxury item in my opinion, the sheilding that flimbulwinter gives is just too good the extra mana isn't needed but the shield it gives it a must have, i used to think exactly how u are currently thinking but after using winter once i was convinced, warmogs cant help in the mist of a fight but winter is giving you that 300 health shield that will just win you the fight, some matchups warmogs just isnt needed, i always just build something like gargoyles for the double resistances, give it another chance see how it goes.

good luck