I was actually just thinking about this potential. Kinda ironic. I asked myself, "What if I HAD gone left just outside the nautiloid as opposed to right?"
...
Is this really an option? I should try it in a new playthrough.
In my opinion the loss of Gale, the crypt and possibly Lae'zel were a big one. But I don't see that it is a very probable flow of the game because it's quite obvious that you should follow the route towards the "Gale waypoint" and further on towards the crypt, led by the road and by the black fog you can erase on the map.
I'm usually very bad in finding stuff in games but even I found the crypt by myself without problems or looking into out-of-the-game information.