1. NO ANIMATIONS - use madden running mechanics, when playing madden it feels like an element of skill is involved in beating a defender, madden you flick once for a simple juke to the left or right, if you flick in both directions you'll perform a faint the sudden change in direction, feels very satisfying to pull one off successfully. RC4 you flick the stick and know instantly that the game decides whether you'll beat that defender or not because it traps you in an animation, madden is free flowing and allows you to exploit the space. This would allow for additional footwork moves ie a goose step, spin move etc.
2. Defending mechanics - linked to my first point you should be able to defend someone who is performing steps and skill moves, look at fifa defending techniques, can hold L2 to jockey the player until its the right moment to commit to the tackle, again involves element of skill and timing for the players. Miss timed tackles could lead to high tackles, missed tackles etc.
3. Diving for tackles & tries - Rugby 08 was good for this, you could dive for someones ankles which would slow them down enough for another player to make the tackle, in contrast to this the attacking player should have a "stumble recovery" mechanic like madden, quick tap of triangle and you dont fall to the floor and continue running, miss time the tap you fall.
Other general ideas
1. A high ball box kick set play, involves the wingers, fullback etc. In addition to this a air contest mechanics should be added, similar to catching in madden. At the moment it's purely chance that your player will catch the ball, which doesnt engage me as a player, I need to feel I have control of even little things like this to really enjoy the game.
2. Rucks I think play fine, maybe just look at the contest, the defense only really switch on in their own 22 and near enough always contest and win the ball. However mid field can be fun as can string a few phases together.
3. Really really picky but very small detail, when converting or drop goaling, make the ball spin backwards.
4. Spiral kicks are the only form of punting it down field, maybe add an extra button to determine what kick you perform, holding L2 + X performs a spiral, Just X performs a normal punt with a back spin. Would also like to see different trajectories of the ball, In fifa holding R1 whilst passing will perform a heavy weighted pass fast moving which skims across the surface.
5. Better ball mechanics, it's a rugby ball, I shouldnt know where it's going to bounce.
6. Line outs are okay, would prefer a flick of the analog stick for power and accuracy of throw instead of a timing bar.
7. Scrums need work, take too long and they're are tactic teams use for penalties etc, could maybe add collapsed scrum element for badly timed meeting of the two lines. Teams with better rated forwards should have better chance of good timing of the lines.
Hopefully this is helpful, just a few ideas I thought would enhance the experience. Look forward to updates in the future!