No one wants to fly to London (Gatwick) with a stop in St.John's, especially on 767, might as well take Rouge - direct.
Umm, WJ is flying 767's direct to LGW from YYZ etc. No need to go via YYT. They are also flying YYT-LGW using B737's in direct competition with AC's YYT-LHR flight (that uses A319's). The WJ YYT-LGW route seems to benefit from a considerably more reliable service - no doubt due to newer A/C with more spares available - so perhaps a routeing via St John's isn't the worst idea in the world anyway?!