Aren't your 18 protection soldiers useful in the expansion phase ?
I mean, nearly nobody can hurt them, right ?
You'd think, but you have to remember that protection is probably the worst defensive stat in the game. Especially without something else to back it up, which hobina's critters lack. Even with 18 protection, that 6+ enc, terrible defense (or merely sup-par on the heavy spearmen), and human HP means that they're still going to get damaged fairly often, and when they do, it's got good odds to wound or just plain kill. Add in the high resource cost and map move 1 and... they're actually kind of bad for expansion. They can manage, but they're not much (if at all) better at it than Hobina's other units. You'll lose some nearly every province and probably rack up wounds like no one's business.
With a bit of testing, I can say full prot 18 armies are doing notably worse than the vans I'm having to rely on for expansion (even accounting for the gold difference), despite the good variation I've got access to being stuck with short swords. I'm sure the formorians are just kind of laughing jovially at both of us :V
... with hobina, I'd probably be trying to mass up arbalists with plain spearmen (or caelian ones) screens instead of sending out those prot 18s to ablate off indies. Gold price is the same, but you'll be able to squeeze out more guys with the lower resource costs, and the arbs will hopefully be able to start building up. Which might not be a bad idea at all considering there's heavily armored formorians on the map, too.
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Bonus points on those riders, though. They apparently turn into sacred mechanical men when they drop, haha! So they're fragile, but they turn into something somewhat... well, equally fragile, but in different ways, with 0 encumbrance and reinvig.