Managing units becomes a little tedious after a while and I'm wondering if viable/safe on my explorer or even my soldier. Since the introduction of miasma it's my belief that automated exploration might be more dangerous for fear of my units running in to aliens or miasma. Not only that but the terrain in BE is a lot more broken up and thus harder to explore than previous Civ games in my experience. I just don't want to waste a unit. Has anyone had experience with this and can automated exploration be something to rely on if not all the time but for a few turns?
Short answer: yes, it is (mostly) viable.
Explorers, by default, will avoid miasma. If they become blocked (ie: there is no safe path to an accessible square that is clear of miasma), then the automation stops and they will demand orders. Explorers, however, have no fear of aliens. Originally, the level 1 purity perk prevented aliens from attacking the squares that your explorers reside in. However, that was recently changed in a patch to double the combat strength of explorers when defending.
Explorers will also prioritize caches that are safely accessible to them, and will start an expedition at a safe tile if there isn't anything more interesting for them to do.
There are some drawbacks, however. Explorers tend to utilize the same paths when traversing long distances like oceans. Eventually, that will even out, but this behavior re-manifests itself when several explorers group together for some reason and end up trapping themselves along the very top or bottom of the map (and disables the automation order). But, I don't find these drawbacks a deterrent to giving them the automated explore order, just be prepared to occasionally guide them to where they need to go.