not really true, the side of 83 is the only which comes close to that, id agree they had six to claim Jan o was a seventh is probably pushing it, yes he averaged over 7 but spent the whole black season at reserve. still arguably the best bl team of all time?
Apart from that the heathens sides were generally top heavy with very weak reserves (Reid, verner , barrett , s Collins etc) but this did allow them to have four genuine heat leaders (Andersen grahame Collins plus penhall/king/pedersen ).
don't disagree with the point u are making though, although there were some pretty awful bl sides too in that era ( swindon of 82/83, eastborne 83 Halifax when kc was injured, exeter of 84 spring to mind)