Two pebble companions will offset a frog companion entirely as well, so you will still get a net profit using Nana to babysit (at least once they are leveled up a little bit, level one companions not so much when they are spitting 30 pebbles at you). Frog swamp is the leveling meta, forget about leveling in gauntlet or campaign and wasting twice (or more) the stamina as usual, frogs take no stamina or personal effort. :P
Most campaign areas worth farming in only need a level 10 wolf & companion pair. Species doesn't seem to matter much once they are maxed, you won't take much damage in most of the low level areas, which can be the most efficient to farm in. Mid-higher level areas where you start to see groups of level 7's, it's beneficial to have something like a jocol/siphoning scratch companion pair, brachus have a low hp/defense stat comparatively and are more fragile.
Here's a couple funky questions to stimulate some more discussion;
Does anyone have any slick tips for fighting campaign bosses? It's almost certainly not worth the stamina investment at the moment to take multiple wolves into the campaign to roll encounters for them (unless you are specifically hunting those achievements I suppose), but if they ever get reward buffs to change that, it would be interesting to see what people's tactics look like.
And then-- are there efficiency breakpoints in lower levels of mining where it makes sense to use a lesser ore for a pickaxe and a higher tier ore for wheels, since the distance seems to scale more dramatically & those higher tier equipment pieces start using more bone paste and ores per item? Using iron picks and silver wheels in the lower-mid tier levels, that kinda thing.