Here is my rune analysis and ranking of LoL Season 3. When Season 4 is out, I will update this article. Hope this will help you on your Rune Builds.
IMPORTANT NOTE: As with any analysis or attempt at organizing metrics of usefulness (Tier lists etc.) This is purely opinion based on my experience at my level of play. What I think are extremely useful runes may in fact suck, or vice versa. Don't take this as law, but I will try and balance opinions and make this at the least a useful thought provoking resource. Also note, I will only be going through Tier 3 runes considering that they are the competitive level and runes matter much less at tiers 1 and 2.
Relative Value and Basic Items' Conversion Table
Explanation: e.g. Long Sword's addition Attack Damage is 10, its price is 400 gold. So the Relative Value is 40 (400 diveded by 10).
More about Relative Value:
(1) Scaling type Runes are counted at its level 18 values firstly and then divided by 3 as final results.
(2) In order to match other runes' results, Quintessence's Relative Values are divided by 3 as final results.
(3) Other runes like Percent Health, Revival and Experience that can not be compared with basic items. Their Relative Values are counted by comparing with certain Masteries.
Rune Ranking and Relative Value Analysis Table
Percent Health (Seal): +0.5% health (C/17.5)
Percent Health (Quintessence): +1.5% health (C/17.5)
Revival: Reduction of time dead -5% (D/5)
Experience (Quintessence): +2% experience (D/8.75)
I will be using a ranking system that essentially means:
S-Rank: If you can benefit from the stat, you should probably be using these runes.
A-Rank: Extremely viable runes
B-Rank: Runes that can be used if you are trying to min-max their stat.
C-Rank: These runes don't offer as much as you'd think, or other stats cover them better.
D-Rank: These runes just don't cut it. Either minuscule benefit, or another rune covers the same stat better.
S-Rank: Armor Penetration, Magic Penetration, Hybrid Penetration
A-Rank: Attack Damage, Attack Speed, Critical Chance
B-Rank: Scaling Attack Damage, Armor, Critical Damage
C-Rank: Ability Power, Scaling Ability Power, Magic Resist, Mana Regeneration
D-Rank: Mana, Scaling Mana, Health, Scaling Health, Cooldown Reduction, Scaling Magic Resist
A-Rank: Mana Regeneration, Scaling Mana Regeneration
B-Rank: Scaling Armor, Scaling Health, Scaling Health Regeneration
C-Rank: Attack Damage, Ability Power, Scaling Ability Power, Magic Resist, Health, Health Regeneration, Energy Regeneration, Attack Speed, Gold, Percent Health, Critical Chance
D-Rank: Scaling Attack Damage, Mana, Scaling Mana, Critical Damage, Scaling Magic Resist, Cooldown Reduction, Scaling Energy Regeneration
S-Rank: Ability Power, Magic Resist
A-Rank: Scaling Ability Power
B-Rank: Mana, Cooldown Reduction, Magic Penetration, Mana Regeneration, Scaling Mana Regeneration, Scaling Magic Resist
C-Rank: Attack Speed, Scaling Mana, Scaling Energy, Armor, Energy
D-Rank: Attack Damage, Scaling Attack Damage, Health Regeneration, Health, Scaling Health, Critical Damage, Scaling Cooldown Reduction, Scaling Energy, Critical Chance
S-Rank: Ability Power, Health Regeneration
A-Rank: Attack Damage, Armor, Magic Resist, Movement Speed, Magic Penetration, Hybrid Penetration, Mana Regeneration, Scaling Mana Regeneration, Life Steal
B-Rank: Scaling Attack Damage, Gold, Attack Speed, Experience, Health, Mana, Critical Chance, Armor Penetration, Scaling Health Regeneration, Spell Vamp
C-Rank: Scaling Ability Power, Scaling Magic Resist, Revival (Reduction of time dead), Energy Regeneration, Scaling Health, Scaling Mana, Cooldown Reduction, Percent Health
D-Rank: Critical Damage, Scaling Armor, Scaling Cooldown Reduction, Energy, Revival, Experience