I'd tend to agree with Tomkins sympathisers with respect to his attacking play.
The Warriors halfbacks have individually benefited from having him in the team, but they have been really poor at making the best use of him for the team as a whole - they've been better at running him out of space, or simply not passing to him at all than they have in regularly making use of him on the fringes. We've seen glimpses of what he can do with the ball, and some of his play really is top drawer, but not enough. However, this is partly because of the way he's being used.
However, the main problem is that Tomkins is simply not a quality fullback in defence. His defensive efforts on high kicks and reading the play and getting himself in position in the defensive line are not up to scratch on a consistent basis. Either the Warriors live with those faults, or he'll need to improve dramatically or move into the halves where he won't be exposed in quite the same way.
Frankly you cannot get away at the top end of the NRL with such inconsistent (and sometimes downright awful) defence. When I've pointed out before that top NRL fullbacks are great attacking players, its not at the expense of being solid in defence - Slater is generally superb, Inglis pulls off some amazing saves, Hayne is great - the list goes on. They do make errors - sometimes very costly - but not at the rate Tomkins does, and they will generally offset that by making massive defensive plays later.
It also gets shown up for England against Australia - we just can't afford to give away tries for nothing against them, but I've yet to be convinced that under pressure Tomkins isn't highly likely to give away one or two soft tries. If Sinfield isn't picked I'd go with Tomins and Widdopp in the halves and Hardaker at fullback.
BTW, it is much easier for forwards to make the transition to the NRL - it should be as their job is much simpler.
