Mistwell
Crusty Old Meatwad
It's a role-playing game, so the enemies are sentient. They make decisions based on their own observations and internal logic, as the DM interprets it.
If your DM is meta-gaming, and having the enemies attack whoever the DM wants rather than whoever they think the enemy would want, then you have far worse problems than choosing which feat to take.
I don't know about you, but I'd rather take the 90% chance of hitting for half damage than the 10% chance of hitting for full damage.
Barbarians are in the upper half of ACs typically. I don't know where you're getting your numbers, but they don't mesh with any guides or pregens or anything I've seen.
Plus, you're simultaneously arguing immortals and best target to choose to attack. It's a mutually exclusive position. Either they are not killable and therefore intelligent targets wouldn't target them, or they are worth attacking 90% of the time. Pick a position.