As in maybe an item that actually gives more MR?

As a tank I'm busy trying to build to protect myself from people who are dealing % hp magic damage, once I have a negatron there is literally nothing it upgrades into that gives more MR (except 5 more for about 1400 and a bunch of other stats I don't need)
So yay I can build health right? no because its % HP magical damage what am I gonna do against Eve or DFG or BFT or liandras torment etc.

Literally the only gold efficient thing to do is to stack several negatron cloaks which takes up slots and gives me nothing to upgrade to.

Even last season at least there was FON which gave +76 MR I just have never understood why there is not items that give large amounts of MR. I'm just sitting there as a tank and trying to figure out what to upgrade Negatron into and none of my 4 options really give me anything I want.

Banshee's Veil
Spirit Visage
Abyssal Sceptre

ALL excellent items on tanks. However HP is just as effective (if not moreso) for shutting down non % damage casters.

For everyone else?

Merc's Treads (almost obligatory)
Bulwark (a staggering 60 MR btw)
Guardian Angel
MR/lvl runes

Totaling (on most champs)

181.5 MR

If you need more any of the first three items I stated will be excellent. Bonus points: Bulwark+GA also give you combined 80 armor (most tanks w/ that will be sitting around 200 armor to go with their 180 MR and you did so using only 2 item slots and boots).

Edit: The HP5 on Warmog's is a a strong counter to the degeneration on liandry's

I'll just leave this here...

http://na.leagueoflegends.com/board/....php?t=2868460

Banshee's Veil still completely negates any one spell, no? Spirit Visage still amplifies regen, gives health, and gives CDR, no?

% Max HP damage isn't that common on casters, and even with Torment showing up now you have to consider Magic Penetration got significantly better as well - and Torment also counters magic resistance, so you shouldn't just swear off of HP for countering casters. Base damage and +AP ratios still deal flat damage for just about everyone, so building a solid amount of HP with those resistances isn't a bad idea - and things like Banshee's Veil and Aegis give you health and MR.

The only thing that really changed is that HP+MR is a hurdle casters can overcome end-game just like auto-attackers can overcome HP+Armor. I wouldn't call the capacity to " not die ever to burst casters" that bad either, burst casters have trouble toppeling turrets, inhibitors, and taking global objectives in general that auto-attack reliant champions don't.