Is it better to have a "generic" tier 3 rune page or a specialized tier 2 rune page?

Generic Examples:

* AD: AD Quints, armor pen reds, armor yellows, magic resist blues * AP: AP Quints, magic pen blues, armor yellows, magic resist blues

Obviously champs where these two setups are the "specialized" version are except from this.

By "specialized", let me explain with an example. Nasus really loves early CDR and sustain for best stacking. Is a Tier 2 rune page built for early CDR and sustain better for Nasus than a Tier 3 generic?