One problem, imo, is that the movement system makes it very difficult to scout ahead. Therefore you have to lose and save and reload several of the fights at least once -- often more than once -- to figure out a surival tactic. Many encounters even seemed totally unwinnable the first time I stumbled into them. After several restarts I know that, with enough foreknowledge, and luck with the dies, it is winnable. But this method -- having to lose one or more times before being able to win -- IS quite frustrating.
It's rumored (or maybe confirmed?) that when the game is released out of Early Access there will be a choice of difficulty settings. Presumably we're playing on the "Normal" or "Experienced with DnD games" setting, and there will be an easier setting below that. And something even harder for masochists, or those who already know every encounter inside and out.
So we're playing at an encounter level that gives Larian the best feedback on what is and isn't working with game balance. If it was any easier -- if we were roflstomping every encounter -- they wouldn't have as much player feedback to work with. The current difficulty is also a good way to find out where players have found exploits and other ways to cheese the combat, like the Multiple Alpha Strike mentioned above. And then they can decide to either remove those exploits or leave them in.
Personally, I haven't found the combat super difficult except when I wandered into areas in Act 1 where it's obviously intended to be a geared-up level 4 encounter and I'm not there yet. I'd rather have the game designed this way than with a "flat" difficulty where all encounters are the same, and after reaching level 4 every combat is a cakewalk. It keeps the challenge high.
About the only real frustration I have is with strings of bad RNG rolls, especially with spell attacks. It's a bit immersion-breaking to have the mage or cleric in my party miss spell attacks so often in a row. I guess it's better than having it hit every time and needing to be nerfed for balance, but it still has me yelling at the monitor when it happens.
