Not as a core item mind you, but for when you need extra MR. I'm fairly certain the passive applies the carnivore, and it does quite a bit for relatively little cost since the season 3 buff it got -50 mr, 200 health, 15% cdr, 20% bonus to all healing and drain effects on yourself- and seems like it would synergize very well with his skill set especially on an AP heavy, support Cho, with will of the ancients.

I could be wrong though as i am new to Cho'Gath and not very experienced with theory crafting builds anyway, so please give me your view on the subject and tell me what you think are more viable options.

It is good in tandem with glacial shard, you build whichever you need first, then you build a warmogs and people are so damage focused they derp on pen and say "why you so hard cho?!?!?!" Then cry OP. it is fun to fight people that don't suck but also don't realize that bit of info... That armor pen and mag pen is always a great idea to ramp up damage....