Tank stats in ARURF do nothing
I play Yorick, new to the champ, against a full magic damage team, so I build full MR. Adaptive, Spirit Visage, and Negatron Cloak. Enemy mages build 0 magic penetration, just Rylais/Liandrys/Deathcap. Still die within 3 seconds to any of them (Teemo, Cassiopeia, Annie).
This mode is way too one-shot heavy, if you aren't the one doing the one-shots you're the one being one-shot, it's that simple.