Hey, welcome to the forum…
Not much info to go on here, but based on my own experiences your system should be getting at least 60fps on 1080p with everything set to low. I have an i5-7500 with a 1060 gpu and I get almost 75fps 90% of the time. Unless its a known problem (see below), I very rarely see less than 60fps.
I am assuming you have all the latest patches, drivers etc installed.
There are known issues in the game with certain locations and skills/effects/minions that slow down fps dramatically. For example, poison pools all over the screen or multiple lightning procs or lots of skeleton minions running around - even a big pull of mobs can drop frame rates dramatically right now. Optimisation of these are being worked on (and improve with every patch) but in most cases the game is still easily playable on a system like yours.
One thing also, LE is pretty CPU (not only GPU) intensive so if you are doing other things on your system at the same time as playing, there will definitely be moments where you suffer fps loss.