To say shapeshifters are a crapshoot is an understatement in my opinion. But you may be pleasantly surprised, who knows.

I've had 2 transmuter explorers and they did alright, mostly at higher levels. It would probably be more survivable than a bard in 1-on-1 stationary fights, but worse in places where the creatures tend to wander or group together..

Other explore options you might consider...

Thieves, especially with gentle walk, can stroll unhindered through most aggressive areas. You need to be wary of the creatures that murder or otherwise outright attack when you walk in, but if you survive to flee you will probably be ok. Thieves have a harder time actually killing ultra-tough creatures without creatively using knife/flee spam with various maladictions when they rest, but can steal many handy items without having to kill at all. Scrolls are huge for getting more out of their travels here.

Paladins, have the tools, strength, and healing to explore pretty much anywhere and slowly whittle away creatures in areas much tougher than normally possible. If you have progged gears or virtues, even better. Many imms frown on paladins that vanish for long periods of time, selfishly exploring and looking for shinies rather than stamping out evil PCs, however. Request makes killing key mobs for nice paladin-friendly gear unnecessary as well.

Assassins, like paladins, have superior defenses versus mobs, good detections, vanish is great for eluding tracking mobs in many areas. The biggest problem with assassins is that you will either not be able to take advantage of most of the magical goodies you come across, or you will find a lot of gear you probably can't put to use anyway.

Druids are like paladins with their healing and defenses, but can also bring a pair of beefy pets to the table if they aren't locked into a civilized area. Their maledictions and treeform/forest haven are good for hit and run against creatures normally way too strong to be killed otherwise.

So, there's a lot of good combos useful for exploring. Goodie conjurer is the stereotypical one, but I found my elemental died way too often in the fights that mattered, and it takes forever to kill things with just an archon in your pocket.