Puzzles, riddles, and other challenges of brains and skill are okay in games that are not all about them, as long as the really challenging ones are not required to complete the main quest. After all, games that have a finish are less fun if you are unable to complete them.
I pretty much agree. Stuff like this is best served for side quests with a nice reward at the end for completion. Nothing like a good dungeon, with a puzzle to solve and traps to avoid, with a nice (trapped) chest of loot at the end.
Building an effective generalist is possible, though it does increase the difficulty in the early game.
Why? You can respec in Divinity 2 so you should be able to run whatever you like at the beginning, right?