I've been revisiting Path of Exile (PoE) with the latest expansion, Prophecy. My necromancer witch is into Merciless difficulty, after completing Normal and Cruel.
Commander of Darkness node in the Necromancer Ascendancy class, which adds resistances when I'm using an aura, the 20% Cruel resistance hit didn't cause me too much trouble. But the extra 40% in Merciless is another matter. Fortunately, gear starts to drop with higher resistance values as the levels increase. I haven't quite got the right combinations to max out all of my elemental resistances, but it's close.
One reason I'm still looking for that perfect gear is that I'm playing this character with only the items she buys from vendors or finds during play (this is known as self-found). There's a large trading community in PoE, and if I wanted to shop around I'm sure I could find the perfect items. I like the challenge of the self-found character, though, at least for builds that don't require specific unique items. Whenever I decide to play some other characters, I'll likely look into the trade market.
When I completed the Labyrinth back in Cruel difficulty, I chose to add the Mistress of Sacrifice node from my Necromancer Ascendancy class. It increases my skills' duration, and allows my Flesh Offering skill (added movement/attack/cast speed) to affect me in addition to my minions. That really makes a difference in how powerful my witch feels! My Raging Spirits last longer and do more damage, my Zombies and Spectres are running around at light-speed, and the added movement speed helps me keep out of the way of whatever nasty stuff is trying to kill me. Most enemies just melt away under the onslaught instantly, with bigger rares taking just a bit longer. Unique monsters still survive for a while, but I've not had much trouble for the most part. I've yet to face Malachai at the end of Act 4 or Izaro in the Labyrinth at the Merciless difficulty level, and haven't even considered end-game content like Atziri. But everything in the normal zones and early map areas has been fairly straightforward to finish off.
Another build change that I decided to make was using Chaos Inoculation. This keystone makes you immune to all chaos damage, which is a pretty useful thing in a lot of end-game areas. The downside is that you are left with only one life point, so you have to protect that one point with your energy shield at all costs. I've managed to get around 5500 energy shield, and a few thousand more should be possible as I find better gear. One reason I did this was that I'd already found a Geofri's Sanctuary unique armor, which has decent energy shield plus Zealot's Oath for extra shield regeneration. Thanks to a fortunate prophecy, I was able to get five linked sockets in that armor, so I'll be using it for quite a while.
Once I made it through Act 3 in Merciless, the Eternal Laboratory opened up. This is the endgame system for PoE, where players use maps (dropped like any other item) to open new areas to explore. (And by explore, I mean slaughter everything that moves, of course.) Maps can have modifiers like any other item, which generally make things more difficult on the player by buffing monsters or limiting player abilities. Maps use the same currency items to set those modifiers as you'd use on your gear, so you have the opportunity to set the map modifiers to something you can handle. I really like the system, at least initially. Once you've leveled a character into the mid-80s, it becomes pretty difficult to find maps of the appropriate level, and that's not a lot of fun. But I'm usually tired of playing a character by then anyway.
There's a whole set of prophecies that apply only to maps, plus many of the familiar prophecies can also be found there. On top of that, there are map-specific Ascendancy Trial areas. Plenty of things that are new to me, even though I've completed the story mode through Merciless. (Except for that final Malachai fight.) I died a few times while figuring out those new trial areas, which are quite a bit tougher than the trials you find in the regular zones. Once you know what's coming, you can certainly make it through, but learning can be a rough process!
As for the main map areas, I've only done the lowest-level maps thus far. To this point, almost everything has been fairly easy, even with the monsters getting buffs from the map modifiers. Here's a quick example of the horde eating the Blacksmith boss, for example. I did have some trouble in the Pit Map, which has a difficult final boss area with hordes of extra monster spawning. That's bad for a necromancer since all of my minions get distracted by the extra spawns, rather than killing the boss quickly. That's the only real trouble I've seen so far, though.
I'll probably keep playing this witch for another few levels, at least into the next few tiers of maps. I may start thinking about a different character, too. I've got quite a few interesting unique items and skill gems in my stash that are begging for use!