Performance Issues

Hello,
I've been playing Path of Exile for over 50 hours now and have made it to endgame.
Since the beginning i've been having performance issues.
They weren't a problem at first but the longer i play the worse they become.
My character is lvl63 right now and it's slowly making it into the endgame.

My Notebook is capable of running this game at lowest settings (not including texture quality .ini lowering) at a stable rate of 120 FPS on 1600x900 resolution in towns. Unfortunately it's way worse in combat. The game drops to 40-50 FPS when fightning packs of monsters. I'm running a pure reave build so the effects shouldn't be a problem, but it becomes worse.

FPS drops harshly to 1-15 under these circumstances:
- initiating a Strongbox
- attacking 50+ monsters with one Reave at once
- having alot of corpses on the screen
- playing in parties
- seeing alot of different spells used by huge number of monsters
- fightning Malacai
- Dominus Rain

PC specs (Asus N550JV notebook):
- Windows 8 64-bit OEM
- Intel i7 4700HQ (quad-core 3,4ghz)
- Nvidia GeForce GT 750M (4GB DDR3 version)
- SATA 1TB HDD 5400rpm
- 8GB DDR3 RAM

I'm capable of pretty much running almost any game out there with medium settings on a stable 30 FPS (not including Witcher 3). There shouldn't be a single problem with this game's performance.

Modifying settings doesn't help at all. If i turn everything on i'll just have stable 60 FPS in towns instead of 120. It will drop to 1-15 anyway. Lowering the resolution doesn't help either.

More info:
- installed all windows updates today
- updated all my drivers today
- i have no antivirus, firewall or other software that could be creating problems with the game
this includes Windows Defender, Windows Firewall, Aero and other similiar things
- i defragmentated my disks even tho they were barely fragmented (6-8%)
- i'm literally only running steam and PoE at once, nothing else
- power options are all set to 100% processor usage at all times
- power options have no power saving allowed for anything (even disconnecting USB ports)
- i have a semi-private ISP that provides network for only a handful of people in my district.
it's a 120mbps internet and is pretty much always working greatly
http://www.speedtest.net/my-result/4619157141
- my rig runs: Dota 2 (60fps stable max settings), CSGO (200-250fps stable on lowest), Skyrim (30fps stable high-medium custom settings with a huge amount of HD texture mods [4GB vram] and a weak performance ENB)

I've used CPU-Z and their performance monitor to see how much of my rig the game uses. It reported 60% GPU peak usage and 20% CPU peak usage when the game was running at 10 fps. The game utilizes Nvidia Optimus and my quad-core so it's not a problem on that side.

How can the game have low framerates if it doesn't even use my rig to it's full potential?
I really love this game. I have spent so much time past week on PoE. I was even willing to even start buying cosmetics, but the FPS problems are really killing it for me.

I'm willing to try everything that could possibly help me (not including buying a new rig tho).