Hmmm... I guess the problem of potentially being underlevelled for the final boss areas could be solved by having a dungeon section explicitly mentioned as leading towards the boss, but before the point of no return with enemies of the appropriate challenge level, so if it's too tough, players can go back and do other things until they're ready. If they try and exploit the system to go ahead before they can handle it, well, they've been warned already.
As long as Larian does a few different playthroughs with various amounts of content completion, I trust them to get a good balance.
I would prefer to hit the level cap sometime in the 70-85% content completion range, but not at, say, 98% when all that's left is the final dungeon. Getting it too early could make things boring., but that can't be helped in a huge world with respawning enemies like Fallout 3. Getting the level cap too late doesn't give you the time to enjoy it.
