For me the worst "battery drainer" on Motorola Droid 4 (on LineageOS 14.1) is low 3G signal. Not medium but low, on the edge of signal drop.
Recently I was in place where signal coverage was really poor and I had to workaround battery drain by switching to 2G only. I still was able to browse most of websites using Opera Mini (although I switched its connection mode from HTTP/socket to HTTP as I found it working better on 2G).
Beside these "extreme" conditiions my screen on time is in between 4-5 hours and I charge battery every ~24h.

@Macros @t-b
Have you tried disabling zRAM and enabling SWAP on sdcard instead (not sure if it's enabled in SailfishOS) and enabling GPU rendering in programmer settings?
These "tweaks" significantly reduced lags on my device (of course keeping its low CPU power in mind).