The ring field is actually a fall back. Due to the customisation options it's possible that someone might create a match type or power play where outfielders aren't allowed. Without that field the AI would fall over in such circumstances as there wouldn't be a field it could use.
It's an error in implementation that it's being used in other circumstances and that needs looking at.
regarding fields with nobody behind square on the leg-side, what formats and circumstance?
i believe most or all of the first class fields have a fielder behind square. often it uses a "square" (which despite the name is well behind square) rather than a fine leg / deep fine leg, which is something i've set because i find that position can cover more ground going finer or squarer which is helpful in attacking 6-3 fields.
the logic of AI field choices is certainly something that could have been better in all 3 games. unfortunately, it's also an area that BA haven't engaged on in beta. i have asked directly when they will use certain field types, and when they will switch attack type, but they haven't answered.
regarding batting, it's certainly more forgiving on slogging and that is disappointing. one of the strengths of 14 and 17 was forcing you to play nicely or knowing you'd run of luck. again though, this is something that i think was better before the post-release patches. (though i know
@WealeyH was complaining about lack of edges in particular before that.)