Enslaver - Luck affects the Normal > Magic > Rare > Epic > Legend chance to drop for Pets like it does for Items. but the Legend Pets are still rare. I have gotten a few Legend Pets outside of the Enslaver Feat, so it is possible.
Cartographer - killing Cartographers and collecting Maps Feats are the only way to get Legend Maps.
An Eternal Farm Build with two Nadroji’s Bonus affixes will increase your chances of getting Eternal Pets and Eternal Maps. you could make an Eternal Farm Build without the two Nadroji’s Bonus, but having them increases the spawn rate of the Enslaver a little bit.
here’s a thread on improving chances of getting Eternal Pets.