As stated previously NTRP rating has much more to do with winning matches. I can tell you that I have played in 4.0 tournaments and done fine and my UTR is just under a 6.5. With that said, I don’t think either of us are anywhere near 3.0.
Maybe our volleys are close to 3.0 though haha
3.5 This player has achieved improved stroke dependability and direction on moderate pace shots, but still lacks depth and variety. This player exhibits more aggressive net play, has improved court coverage and is developing teamwork in doubles.
4.0 This player has dependable strokes, including directional intent, on both forehand and backhand sides on moderate shots, plus the ability to use lobs, overheads, approach shots and volleys with some success. This player occasionally forces errors when serving and teamwork in doubles is evident.
I used to play with a guy, former college player, and he's in his upper 60s today. He hits heavy, hard shots, is very, very smart (he quickly figures out what kinds of shots and placements you don't like), has the typical hard first serve and kick or slice second serve, and he has a killer volley. If you pop it up to him in doubles, you'd best get out of the way (or your partner should get out of the way). He's a 4.0 player but a falling 4.0 player due to age. This is a 4.0 player without any obvious flaws in his game.
I've seen lots of 4.0s with obvious flaws. Some don't have a reliable overhead. Some can't volley - I have a friend on a college team, has heavy powerful topspin groundstrokes, very fast, very tall, huge first serve. But you have to hit a drop shot to get him to come to the net. He won't go to the net voluntarily and his volley is poor. I would see him pinning you back six to ten feet behind the baseline in a match.
Another guy that I've hit with was a good junior player. Has a radar-tested 120+ MPH serve. Tall guy, very fit but he graduated from college and is working as an accountant and spends a lot of time playing basketball. This guy also has the heavy, deep topspin shots but he can volley too. Again, a falling 4.0 but that's because he's doing a lot of other things in his life.
When people ask about depth and pace - it's for good reason as 4.0s usually have depth and pace. It decreases the opportunity to get attacked effectively. Even the pushers have at least the depth. The lack of pace is intentional.
I'm in NH. LeeD has suggested that I'm a 3.5 to 4.0. I do focus on pace, depth and footwork. For me, depth is more important than pace; but if I have a good setup, I'll just smack the ball.