I understand the desire for penetration. But the sectional density of .300 was established ( I believe) for dangerous game. After all, the most popular loads for the .30 cals are the 150,165 and 180 with the 180 being reserved for larger game over 600 lbs (Moose, Bull Elk, etc.). In fact, I would guess, of the calibers less than .375, none of the most common bullets have a sectional density of .300. A .358 158 grain bullet was used successfully in the 1930s out of a .357 magnum to take much larger game than we would attempt today with it. A 180 grain bullet, constructed properly would likely still kill even a large black bear from nearly any angle (especially of the TSX variety).
I do concede that the .358 is a niche cartridge, but I wouldn't relegate it to throwing bullets as penetrative as a playdough teacup either. I personally think with good bullets in the 200-225 grain class, it competes rather favorably with a lot of other cartridges. I think it was a solution looking for a problem when it was introduced (Like pretty much all new cartridges introduced in the past 30 years). But there are enough of us to keep it alive. Even if we are relegated to running .308 brass into our .358 dies...