I've played 10 match 5 with Regroup and 5 without. When I played with Regroup the opposition team had more Highlights compared to when I've not used it. So decided not to use Regroup anymore.
In case of CWB I actually have the "Dimond" players that you've described earlier. They both have Aggression, Concentration, Decision, Teamwork, Work rate and Stamina averaging 13 or more. Last season they were my most assist providers. I use CWB because when sometimes there is no space infront of them to run the cut insides, that's what I like about the most about the CWB role rather than traditional WB's. I also use Mark tighter instruction on them.