Your comparison of the game with IWD suggests that what you want is a "set of possible actions" that is much smaller. It's a 3E-like, not 2E-like, system, it really is more complex, no doubt.
I was just writing the following, and you are right:
"One significant difference I see in IWD is that due to the way spell memorization works, a caster (along with all other characters) has only a few possible actions he can execute in a round. In PoE I usually have a choice between at least 15 different spells at any time during combat, and non-casters have many modal or active abilities. In IWD it's just "Turn undead", "Lay on hands", and that's pretty much all I need from my non-casters. Combat is faster, with less pausing but still intense, unless everyone has bad rolls in which case you stare at the party and enemies waving weapons at each other, which does feel dull (but I still prefer it to PoE's combat)."
You can also maneuver much more, due to the lack of engagement, enemies switch targets less predictably than in PoE too.
So, yes, PoE is more complex, but only tedium comes out of this complexity.
A major advantage of the IE games - the asynchronous individual rounds of the IE games are waaay better than the impossible to follow irregular intervals in which PoE characters preform actions. This has a big role in making combat easier to follow in the IE games, and I used to tell this to Obsidian during the Backer Beta days. Let's take a "simple" (PoE "simple") example:
9 characters are on screen - a party of 6 and 3 enemies.
Character 1 has .9 s until he can take action
Character 2 has 1.2 s until he can take action
Character 3 has 1.6 s until he can take action
Character 4 has 2 s. until he can take action
Character 5 has .5 s until he can take action
Character 6 has 1 s. until he can take action
Enemy 1 has .6 s until he can take action
Enemy 2 has .8 s until he can take action
Enemy 3 has 2.3 s until he can take action
Your priest is Character 5. Your fighter is Character 1 and is near death after being hit by Enemy 2. You have no way to see either of these times, so you can't really tell if it's better to use your priest to cast healing on Character 1, or a hitting spell on Enemy 2. The indicators, while you are paused, do not give you any hint as to how long it will take for the recovery times to pass. You just see the lines, you don't know how fast either one of them is decreasing in length (one of the many glaring mistakes in the UI, but don't get me started on that).
In addition, if you are going to cast a damaging spell on Enemy 2, you have to take into account your chances of hitting him, because spells are based on Accuracy, but what if you are under the effects of a debuff, that lowers your accuracy? Should you: 1) Cast healing spell now, disregarding accuracy; 2) Cast damaging spell now, disregarding the debuff, or 3) wait for the debuff to pass and then cast the damaging spell?
This example uses just three characters and it's a pretty standard situation. So, who's volunteering to make all those calculations, in every battle? I thought so.
And this is what passes for combat system in the IE games' successor. The short way of describing it I can think of is "clusterfuck". And I know I'm not going near any other game that uses this combat system. I hope I've made it clear where I see the problems. Mainly in the fact that the player is overloaded with information to the point where it becomes a better strategy to just disregard the ruleset and try to brute force your way through a battle, which works in 90% of battles anyway.