For a Tank, Shen's base armor is pretty low

Shen's heal on Q is the only thing that evens the scales in shen's favor. Now that its getting nerfed (which I think is low blow for Shen) He will be no more tankier than Fiora. Riot claims him to be "a bit strong" while they have some of the most op Champs running around on the rift patch after patch without getting nerfed. It took them almost forever to nerf Irelia, now we have to deal with the likes of Juggernaut Darius. I swear you rioters suck at balance and if you listened more to the community and wouldn't play favorites, this game would be atleast 2 times better.

TL;DR Shen's base armor is too low for a Tank, (especially for a non-ability spammer) and his Q heal was the only thing allowing him to trade other top laners who do way more damage.