So, Cameron, Kennedy and Darling have roles where tackling is not their main role? I can understand that kicking goals is important for a forward, ruck taps for a ruckman, spoiling for a backman...but, tackling is meant to be for everyone isn't it?
Watch Sandilands, 36yo, 211cm, huge turning circle, lumbering...but he always chases as hard as he can, tackles with intent. It can be said tackling pressure is not his main role but he sure as hell will always give everything to put pressure on the opposition.
I really rate Cammac but he has to get more aggressive when he hasn't got the ball. When you are not getting the ball, for whatever reason, manic pressure (see Ballantyne) is what you can do. Every player is required to tackle and pressure the opposition. When you haven't got it, get it back, or at least make it as hard as possible for the opposition.