Games that are more complex than PoE

Sacred 2.It had less skill freedom than POE and a lot less intuitive but there was a lot of complexity.Some of the complexity was hidden and you only discovered it by building up skills/passives to high levels.Of course complexity doesn't mean more combinations necessarily no doubt POE has more builds that can be made than S2 but individual aspects were complex.

I would say POEs system is a lot easier to understand than S2 despite the passive tree.In fact I'd say people coming from S2 would be a lot less overwhelmed by it.

To tell the truth, I found Sacred 2 quite dumb, there were too few utility skills, and most of the time you only used a couple core skills. The customization was good, but it fell short in some other areas, like quests and immersion.

I'd say most roguelikes are more complex than PoE. Just to name my favourites:
Tales of Maj'Eyal
Dungeons of Dredmor
Dwarf Fortress

Don't forget NetHack.

I wouldn't say these games are more complex, perhaps on par with PoE;

Diablo II (I will not state D3 because D3 sucks and I want my money back, but anyway)

Baldurs Gate II or Icewind Dale

Dungeon Siege II

hmmmm...

I miss games from the 90's.

Hearts of Iron III.
You have to think about so many things, Diplomacy, Supplies, Fuel, etc. The first time i played it i was like "Help" only after about 30 minutes of help from a veteran player i managed to play the game.