ok, that makes more sense now, thanks.

Thanks a lot for the spreadhseet DooOoom (sorry i had to abbreviate :P)
I wanted to set something like this up and I am glad you did already.
I like that it is easier to modify than another Item efficiency spreadsheet I have that is based off of "cost" rather than "value" . Ideally having the cost listed near the value box for frame of reference would be awesome.
I agree on the MR situation...There are way too many armor items now...the loss of FoN is making me sad since now the highest MR items are the slot efficient (but cheap) Spirit Visage that isn't really worth it unless you have some kind of healing (ie bad for my main Amumu) or Bulwark which is 3200 gold and doesnt build out of a single negatron cloak that I can hold onto for a while. While for armor we have the new Locket, Spirit of the Golem, Iceborn/FH...or even Randuin's which you seem to have skipped. I still have no idea what my builds will look like but I think making Locket my first major Item may be helpful.

Also your guide is pretty sweet, I have used it many times, sadly I am not that great with him still. Would you value stats about the same for a tanky type of Amumu.

amumu is weird in that he's part bomb part tank. I think you should build him less tanky than maokai for the simple reason that once his ult is down there's no reason for the enemy team to focus him. Although he does need some tank gear so he doesn't get poked down, and his ap ratios aren't too good... he does fills the support/aura role pretty well. But its not like maokai where you need to stay alive long enough to arcane smash over and over and over and over and also keep your ult up as long as possible.

I'd say abyssal scepter is core for amumu, and i'd be more likely to build sunfire cape... and I'd never build warmogs. Otherwise the builds are probably similar, you'd still want and locket and maybe aegis/bulwark.... the combo of locket/abyssal seems like a solid mid game goal build to me, you get health/armor from the locket, plus magic resist and damage from the abyssal... so a good mix of stats... if i played amumu I would probably build locket and abyssal scepter as my first big items.

for stat valuation i'd value auras/actives higher, magic penetration higher, and otherwise mostly the same.

Darius Guide coming soon.

New Spreadsheet, this one is for Darius:

edit: updated spreadshet

You underestimate how strong Maokai's passive, it's half his tankiness (along with his ult). It's basically up every autoattack in a teamfight. If you get stunned/kited, you can't aa and there goes half your tankiness. I'd say the Spirit of the Ancient Golem is worth it on Maokai, you pay 1600 gold for 500 hp, 30 armor, and tenacity.

Honestly, i'd probably buy SotAGolem every game if locket wasn't so good. They're both nice items but locket is just OP. And they give the same stats so its weird to get both.

I think if locket gets nerfed i may start buying Spirit of the Ancient Golem most games, but until then...