User blog comment:Double Slap/Percentage Statistics- Addition for Statistical Efficiency/@comment-24366122-20140906034241

Issues:

1) You usually want a combination of stats compared to just one stat. For your example of randuins and sunfire cape, randuins definitely raises your EHP more than sunfires. There is no such thing as a waste of armor, as increasing armor does not give diminishing returns. Unless you tend to be building over 300 armor at one shot and ignoring MR which is rare (happens if you go FH, Randuins, Thormail) BUT armor here is not so good because it comes at a large OPPORTUNITY COST where you are better off getting MR or HP to survive burst from mages. Also the example is flawed because sunfires gives armor as well, and if you really don't want the extra 25 armor you are better off going spirits visage or even warmogs. A 25 armor vs a 50 HP opportunity cost is a small matter compared to "do I need the randuins passive or sunfire passive more?" or "Shouldn't I be getting my MR item instead of armor?"

2) Also, by using % statistics you have to ignore many other components of the item. In your example, you ignored the armor and the passive. Ignoring the passive is the same problem that gold efficiency has. In complicated items, lets say triforce, hextech gunblade or nashors tooth, that give a wide range of stats but not too much of any stat, % statistic calculations would leave them at the bottom of the table for ANY stat that they give. Actives or passives that are really good, such as spellblade or mikaels crucible active are totally left out.

3)Even if this table was available when you are midgame, you have to compare these items across possibly many other items and on different parameters (lets say you want AD and crit) because as said before - you want a good combination of statistics on an item, rather than 1 statistic alone.

4)With both gold efficiency and % statistic efficiency being looked on at once, it will be terribly confusing if you are trying to select items midgame. "This one is % statistic for HP more efficient but not gold efficient? Oh the other item is gold efficient but does not give enough % statistic efficiency for HP but has a passive? Which do I pick?"

5) Loopholes. Example: You are an AP mage and you want HP to survive some extra burst. Would you buy Sunfires or Warmogs (100% health LOL)  or even face of the mountain that are statistically more efficient for HP or rylais crystal sceptre which is less statistically efficient? Why not consider hourglass seeing that it has a sick invulnerability active that would be arguably more important for non mobile siege mages? (Lux, Brand) Or why not GA for a revive passive? (The correct answer is zhonyas, GA and rylais are way better than the others under most circumstances)

In conclusion, this % stat efficiency is not that useful especially in game. Also, you should be buying items that either synergize well with your champion, for example spirits visage on mundo, Deathcap on any AP mage, have all around good passives(banshee's veil or GA), or have good synergy with other items. (IE and PD, Liandries and rylais, Dcap and Void staff). Stat efficiency (This item provides AP, MR and Mregen which basically every AP needs) and slot efficiency (basically pick items that you would keep for your six item build) should be looked at as well.

Good luck.