Originally Posted by Xypherous
Twin Shadows will add to your core initiation / Spirit Visage will greatly help if you have a strong self-heal (Hecarim or Alistar, for example) and Abyssal Sceptre always helps your team and yourself, depending on who you are.
Although, yeah - I do suspect that Negatron is in an odd spot - it feels like it should be cheaper and give less MR so that its upgrades could also be slightly cheaper or give more MR. The build path for the MR items providing most of the MR you need seems to be strangling how good the final MR item can be sometimes. Not sure.
Well, it's partly to do with the good options for MR items -- namely, the lack of them. Items that provide MR:
- Chalice/Athene's - most tanks don't need the mana regen
- Aegis/Bulwark - goto item, as I said, counters 2 magic pen items from the AP.
- Banshees - The mana is rarely useful at the point it is bought, the passive isn't too useful on a front line champion who gets poked a bunch. Doesn't provide much additional MR by upgrading
- Hexdrinker/Maw - Great on bruisers, alternative to Bulwark for them.
- Wits End - Now more expensive for 10 less MR. Used to be good on some attack speed based tanky champions like Irelia or Shen, now it's just not worth the price.
- Spirit Visage - Better than it was in S2, it's pretty good now, and since it gives CDR and HP it's generally superior to Banshees, especially given the cost.
- Twin Shadows - Underrated, some champions don't really want the AP, though.
- Crucible - Again, the mana and mana regen aren't usually relevant.
- QSS/Scimitar - Most tanks shouldn't be needing the active, and you pay a high price for the active.
- GA - A lot weaker, and starting at a flat amount of health isn't usually what a tank wants. Especially since they aren't tanking while they are reviving.
We have maybe 4-5 viable MR options, Maw, Spirit Visage, Twin Shadows, Bulwark, Banshees, the latter of which probably is just overpriced still.
Compare it to viable armor options at the moment:
Frozen Heart, Iceborn Gauntlet, Locket, Bulwark, Omen, Sunfire Cape, Spirit of the Ancient Golem.
Atmas, Banner of Command, and Ohmwrecker also want to be armor items, but they are rarely good. Zhonyas isn't good on most tanks. Thornmail is highly situational.
So we have at least 6 good armor options, of which they generally provide more armor than the MR options provide MR. Part of this may be to deal with the fact that ADCs have more multiplicative scaling than mages, but the fact remains that armor items provide more options and armor than MR items provide MR.
EDIT: I think overall, there are more earlygame options for MR items, since there are more items that provide MR in addition
to their other stats, but there are fewer lategame MR options when you actually want an item that provides significant values of MR.