If you look back at the polls when Abbott was PM LNP regularly poll in the low 40's 2pp, under Turnbull the once polled 45% 2pp but mostly around 47-48% 2pp. Some how you think LNP would do better under Abbott
The preferred PM polls do serve a purpose, for one it hints to what is the potential problem in a party. Under Abbott lnp poll poorly and Abbott also polled poorly as preferred PM, that suggested that Abbott himself ws the reason LNP polled poorly. Funny enough, as soon as Abbott was dumped and replaced by Turnbull LNP jumped ahead in the polls, that was confirmation Abbott was the LNP problem.
Now with Turnbull polling so far ahead of Shorten as preferred PM, that suggests that he is not personaly the reason LNP are behind in the polls. You could go further and suggest LNP would be polling worse if some one else was leader.
Last but not least, at the last election the polls where close but the fact that Turnbull was more popular was the difference between losing and winning
