I guess many people like new Warmog for crazy regen vs poke. But my personal favourite is Sterak's Rage. The fury passive has 45 sec CD, so it synergizes with mark/dash (40 sec CD). Which means, you have free shield and massive dmg boost ready for every engage.
I like the Titanic Hydra addition because I often find myself in a situation where I'd like more tankiness, but still need damage if I'm AD. Before I could pretty much only get those stats with black cleaver. Warmogs is crazy good in ARAM now. it's hilarious on Soraka because she just heals her whole team while regenning like a mundo with ult. Randuins is nice against ashe/yasuo/yi. Overall I actually like the new item additions. Not so sure about Thornmail though. I've heard people saying it's garbage now but I haven't really had a chance to test it out.
I only build Warmog's on champions that have health-regen as part of their kit (Garen, Mundo, Volibear). But even then, it's not a good first item due to the 3,000HP requirement. After a Sunfire/Randuin, Spirit Visage, Heart of the Mountain, and Locket -- if the game isn't over, then a Warmog's. Maybe.
I'd still remove Warmog's from ARAM (again). The Overlord's Bloodmail is a better fit -- health regen on kill/assists, but not_ LOLHP5LOL_ sustain that Riot has, previously, considered "toxic" for ARAM. Which is precisely why it was removed in the first place.
