I'd like to point out a few things: First, if you're going to level any DoL/DoH, you should level them all. There is a LOT of overlap between the skills, plus for DoH you'll want cross-class abilities to make high-quality items.

Secondly, the point of a retainer venture isn't necessarily to get things you cannot (though exploration ventures can do that...), but rather to help in cases where a drop is annoying to get. Hunting and fishing are probably the best examples, given that both are fairly random, and hunting in particular can be overcamped to hell and back.