Good valid questions, Q. I guess my best answer would be that I've been playing 4 wedges for a few months now and in all that time I can't recall regretting not having it. I've faced shots that would be eagle opportunities if I had it but when you go to 4 wedges you have to commit to smart golf. I'll take an automatic birdie all day over an occasional eagle try.
You have to get creative with some shots like the par 3 at RSG that's 241 from the Legend tees. You can roll it right up to the pin in any wind by punching the driver there. Any kind of helping wind and the 3i plays. Keep in mind I use the Callaway (s) ball so the extra spin plays a part.
On holes like BPB 7 you're always going to be able to roll onto the green from a decent drive with a 3i and top spin. That hole is a tough birdie even with a 3w. Again, a decent wind and you can stick the 3i close. It will carry that trap. It also plays well from the front left fringe with a pitch or punch.
The long par 4 and 5 at CCC depend on the wind. More often than not the par 4 is 50-50 birdie and the par 5 is an eagle opp if the wind blows right. Otherwise it's an easy layup to a birdie.
A side note here on the (s) ball; top spin affects the way the wind works on a shot. The extra spin of the (s) ball goes a long way to offsetting a lot of wind conditions and you can drive shots through it. It also enhances the carry on shots with the wind to the point you have to back off when using it to compensate. It's a learning thing.
When all is said and done, I myself am a bit surprised at the way a 4 wedge bag handles Legend conditions. I'm pretty comfortable with them now but like I said earlier, if I was in some serious competition where every single shot makes a difference, I would have that 3W on certain courses.
One of the things that 4 wedges gives you is the confidence to extricate yourself from errant approaches to the point that you can be aggressive. The R11 3 iron changed it all because of its length and accuracy. So far, so good. :-)