Ask an Aran thread.

You will probably never reach 90 combo with insane attack equips on an Aran. Insane attack equips are only good for the highest level areas.

Higher combos rely on lower damage so you can hit a monster more before it dies.

I assumed it dealt more with the area, mobby areas like deeper in oblivion still seem to get fairly high combos because of the spawn rate and such, even on higher end arans i've seen in Korean videos...