I got a Mountain Grinder of Potency lvl30 and noticed that the non-ability chargeup time is much longer than I was used to with my Abyssal Flamberge of Lethality lvl25.

With the MGP my damage increase is +118.9 and DPS increase is +81.1, whilst with the AFL my damage increase is +105.7 and DPS increase is +115.7