This looks messy, and it will only get worse as teams catch on to the idea that if they don't commit any players to the tackle, no ruck formed, therefore no offside lines appear so they can stand anywhere they like. Its effectively a tackle version of the tactic of not competing at a line-out; the players make sure they don't engage opponents.
Its a difficult one that is not going to be easy for WR to deal with without some Law changes around the tackle area. Some solutions might be
1. Revisit the Offside at the Tackle ELV.
It has its own bad side effects with regard to midfield breaks being undefendable, but there might be ways around that, for example if the Law was written such that, when a tackle takes place
a. a player who is onside at the tackle must not move into an offside position.
b. a player who is offside at the tackle must not remain there, he must commence retiring to the offside line.
c. exception: if the ball is cleared or passed at least 1m from a tackle, a player in the act of retiring is immediately put onside.
and/or
2. The tackler must remain in the tackle zone. Remove the option of the tackler rolling or moving away. Make his only option to get to his feet and remain in the tackle zone where an opponent can grab him to form a ruck. Should also apply to the tackle assist.