With the current price of runes, it is infeasible for most casual players to have specialized rune pages, so what are you guys thoughts on the best tier 3 rune page for someone who plays casters, physical carries, tanks, support, everything?

I've heard HP Quintessences are good. What are your thoughts on the best general-purpose rune page?

I do the following:
Red - Armor penetration
Yellow- HP/Level
Blue- AP/Level

Quint- Have not purchased yet. Will probably go for HP or Movespeed

Health/mana regen, dodge and movement speed are good on every single hero.

Mana regen is no good for Trynd, Katarina, nor Mundo, but otherwise:

Blue: Cooldown or AP (AP helps every hero at least a little, but cooldowns are more universal).

Yellow: Health regen or +Health are the most universal. Dodge is good too but ideally not used by ranged heroes much.

Red: Armor pen is the most useful for those that want it, but critical chance or even crit damage applies to all heroes. Red is the hardest and maybe the first color to diversify in. You really want magic penetration for casters but something else for physical.

Quints: +Health, straight up, is the simplest and useful for everyone, especially early in the game. Movement speed or +XP work for everyone as well.

Are magic pen and armor pen really all-purpose. For example, is armor pen still good on morgana, and is magic pen still good on tryndamere?

blue: cooldown

red: +health/armor: otherwise you would have to decide whether you play more of a caster or physical dps style. offensive values are better here.

yellow: +dodge (the single strongest yellow rune imho)

a conservative, more defensive all purpose rune build.