<"...problems concerning itemizing against magic damage after the removal of Force of Nature are mostly a figment of your imagination....">
Anytime someone tells you that something is "a figment of your imagination", you should disregard everything they've said to you.
Above all else, Trust yourself and your instincts. If your gut tells you something is wrong, believe it!
I like the OP's post for stating, once again, what numerous players have stated since Riot regurgitated their "Pre-Season Patch." The Pre-season patch was supposed to "bring more item options for all roles", it didn't. It took many options away from certain roles, leaving them with little to no choice but to use certain items. Witness everyone's shock and surprise to see Shen with a Spirit Visage. The Pre-Season patch also instituted Role-Restricted Items, thus further limiting build options.
To anyone who complains about the lack of viable MR items to counter AP damage, the resident Forum-Know-it-Alls always respond by suggesting "Runic Bulwark." However, when presented with a well reasoned, mathematical demonstration of why Runic Bulwark is a piece of ****, those same Forum-Know-It-Alls become a vicious pack of dogs, whose only response are childish insults.
The current roster of MR items are all ****.
The Season 3 patches are about weakening champs and taking away choice.