"Spirit Visage is still occupying the slot of “magic resist item you want most of the time”. To leave room for competitor items to shine against magic damage," SV is one of 4 MR items that does not give AD, Armor, or is a support item. I don't see why they want to nerf SV when the real problem is a lack of comparable MR items that puts it as the go to tank item over the other 3 (one of which is Boots) or other gimmicky/situational items.
That would mean admitting Helm is hyper niche and Sceptre is just kind of incredibly...flat. (Plus, only useful for those champions who want to tank up on MR and also deal majority magic damage).
are all situational, yes. But they specifically wanted HP/MR items to be situational, because they want tanks to be resistance stacking, not HP stacking. 
are all fine (its not like you're not taking physical damage anyway). I agree that the other HP/MR items should be better but its not like their reasoning for nerfing Visage was wrong.
Because something something 
+ 
+ 
something something is unhealthy.
