Our bacons are getting pretty old especially on the battery side. After using sultanxda rom that was underclocked to 1958 Mhz i noticed a nice improve of SOT without sacrificing performance too much .
Unfortunately, on every other ROM, changing frequencies trough kernel tweaking apps (ie kernel adiutor) results in Qualcomm mp-decision not behaving correctly, cores not going offline and frequencies scaling pretty much messing up.
This zip underclocks correctly your CPU to 1958mhz, without the need of any third party app, hope you ll find it useful.
Again, all credits go to @Tomoms