Warning: This post should be fairly clean in terms of spoilers (using spoiler tags when required), but posts after this have no such guarantee. Scroll down with caution.
Updated regularly, so it might become 5 complaints, or 3, who knows.
#1. The Ability you gain access to over the course of the plot
By which I mean Tenebrium.
Imagine how frustrating it is to dedicate rather heavily into a weapon ability such as Two-Handed and then realize you would have been better off saving your points and investing in this ability instead. You shouldn't have to be an online researcher or reroll from that far advanced in the plot. If anything, the ability shouldn't be a Weapon Ability at all, but a Defense Ability, protecting you from the harmful effects of that-which-shall-not-be-spoiled... which, of course, you'd need to defend yourself from if you actually plan on holding it.
#2. Invisibility is overpowered
Infinite gold, and never being in a fight you don't want, ever. Really?
Whenever I think of this problem I think of Death Note. Remember how when Light realizes Ryuk, an invisible demonic friend of his, is under video surveillance, he tells Ryuk he can't eat apples anymore, because they'd see an apple disappear into nothingness? Well apparently that kind of logic just doesn't exist in D:OS, because an NPC can be staring right at a painting, watch it mysteriously float for a second then turn completely invisible, as if entering an invisible backpack, and think absolutely nothing of it. It's already easy enough to steal everything which isn't bolted down, using clever tricks such as distractions or timing; it shouldn't be
that easy.
Also, not every battle should be skippable with invisibility. Most of them, definitely, but there should be some enemies out there with nonvisual means of detection (heightened senses of sound or scent) which allow them to detect invisible characters as if visible. This is something which should be clearly displayed, just how Invulnerable enemies clearly display that they are Invulnerable. I'm not suggesting all enemies bypass invisibility any more than I'd be suggesting that all enemies should be Invulnerable. But we do have some Invulnerable enemies, and we should a roughly equivalent number of invisibility bypassers.
#3. Trait dialogue blindness
aka the most frequent cause of savescumming
Until you memorize all the dialogues in the game through repeated attempts, assuming you want to min/max the trait system, you're going to be saving before dialogue choices more often than you save before battles. After all, an accidental death during combat is something you can negate with a Scroll of Resurrection, but messing up your traits is permanent. The real cause of this is that players have absolutely no idea how they are going to effect their traits before they answer a question. It can sometimes be very difficult to determine whether a particular response is Heartless or Vindictive, or if it's Materialistic or Egotistical. Please, please just indicate directly on the response what effect it will have, so that instead of "No, we will not be escorted by the guards," we see "No, we will not be escorted by the guards (Independent)." I am probably just about done with traits at this point, but future players will thank you for having to stare at loading screens less often.
#4. Lockpicking has 5 or bust syndrome
Useless in Cyseal, might be good once you invest super-heavily into it, I don't know.
With my first playthrough I put a point in Lockpicking at character creation. Then rather early I put a second point into it; 2 ability points. I was somewhat frustrated to come across a lot of "Lockpicking level too low" situations, so I raised it again (3 more ability points, at lowish level); I was kind of unlucky with gear, so I didn't get any +Lockpicking items. So then at rank 3 I try some more locks, and... "Lockpicking level too low." Again.
Now don't get me wrong, some of the locks in the game should definitely require 4 or 5 in this skill. But really not the Cyseal stuff; that level of Lockpicking is simply not reasonable that early in the game. Or if you are going to require a hefty devotion to Lockpicking, at least give us some way to realy commit to it, kind of like how you can get really high Charisma early on by taking the Politician talent, and/or equipping the Smelly Panties which are fairly easily found, and/or crafting Tooth items which boost your Charisma further. Either give us the tools, or lower the early-game requirements. No comment on later-game requirements, since I rerolled in frustration.
