Locked out locations

There are indeed missable chests

I'm torn on this. On one hand they are not needed for any achievements or trophies, on the other hand people feel good with a full completion. 

On the other OTHER hand, getting everything is a reward for a thorough player throughout their adventure. 

Many ways to look at this.

I'm actually ok with one-time-only locations, like the Ossuary, given that the game doesn't force you to permanently miss the objects there.

What I really don't understand is the logic of a counter for chests, altars and the % of map discovered if some areas of the bigger maps aren't really accessible. Even in gameplay logic is terrible to put you in the position of choosing between following the main mission with the urgency requested by the roleplaying and exploring every single place so you don't miss a thing.

Example: If I'm searching for the dissapeared elves, I shouldn't "waste time" going around to solve puzzle. But if the game doesn't allow me there anymore after this quest, I really don't have that choice.

Now that I am at the end of the game, I really feel disappointed and let down by the whole experience... (not only for this map problem, although it was the trigger for me)