The cool thing about Mythic is it does both.
You can use it to empower low level heroes for a small group. Or you can add tiers after level 20 working as levels 21-30. Or give out tiers for higher powered characters at low levels.
I too would like to see epic for pathfinder.. but I like a lot of different things Mythic offers. It cane be used for campaign tone.
Your game is one of those that has total caster dominance, and fighters are near useless - give all the straight non-spellcasters Mythic.
For solo games as I mentioned.
Using the Mythic rules for monsters but not for PCs, and give the Mythic to whatever monsters you want to be really scary - because they don't play by the same rules - All Undead are mythic, or All Dragons.
If you really want to run a fantasy earth game, base races for PCs, and any monster (even Orcs) have mythic - most of the antagonists of the game are NPCs, but when monsters show up it is very memorable.
Maybe the PCs are demigods, and no enemies has Mythic - the PCs are really the center of the world.
I know one mentioned in the book was the Mythic ranks were temporary - a blessing from the Gods or gifts given before an epic quest.
That are just ideas that I came up with using the Mythic rules in the first week I had it.
Mythic in addition to just doing "high level" play, allows all sorts of other campaign tone and styles to be used.