Hi guys,
I believe I may have talked about this elsewhere, though perhaps not on the forum. Your team will always commit three players to the ruck. Which three players is determined by the tactic you have selected. These can be selected at any time - even during cut scenes (as can defensive tactics).
We found that a ruck intensity mechanic as well as a second simultaneous mechanic to add or subtract players from the ruck is not as fun and slows the flow of play - which worked against our design goal. In 08 and our previous rugby games, you influenced the contest at the breakdown only by how many players you would add to the ruck. What we observed when people played this phase of our games was that they would simply begin mashing X as soon as they anticipated a tackle. It didn't matter if they would then overcommit players creating holes in the defensive line, their instinct was to mash. We wanted to acknowledge this natural tendency but to add a more explicit risk vs reward element to it - which led to the current design.
As you'll learn, and as Chris learned, you can be punished for indiscriminate button mashing through unintended offloads and through ruck infringements. We also see more structure in the back line as we aren't pulling in more players to support a button mash breakdown.
That said, three players are always committed on defense as well for balancing reasons.
As I've said elsewhere, if this new mechanic proves to be successful and popular, we may look to add an option for uncontested rucks in the future as they certainly are an important part of the game that we would like to see in there if we can include them in a way that supports fast flowing and fun gameplay.