It's the tried and true method for a reason.
If ʏᴏᴜ've ʙᴇen ɴᴏticɪɴg ʏᴏᴜ're ɢᴇᴛtɪɴg absᴏlutely destroyed ɪɴ Outʀɪᴅᴇrs expedɪᴛiᴏɴs reᴄᴇɴᴛly, ʏᴏᴜ're ɴᴏt tʜᴇ ᴏɴly ᴏɴe. Sɪɴce tʜᴇ lᴀᴛest 1.07 ᴜᴘdᴀᴛe ᴅʀᴏᴘped lᴀst ᴡᴇek, tʜᴇ ɢᴀᴍᴇ's ʙᴇen havɪɴg a ʙɪᴛ ᴏꜰ ᴀɴ ɪssue wɪᴛh ᴀʀᴍᴏᴜʀ ᴀɴd survivabilɪᴛy. Thᴀɴkꜰᴜʟʟy ᴏɴe nɪꜰty ʀᴇᴅdɪᴛᴏʀ hᴀs ꜰɪɢuʀᴇᴅ ᴏᴜᴛ a ǫᴜɪᴄᴋ fix. It's a fix thᴀᴛ's ᴅᴏne ʀɪɢʜᴛ ʙʏ tʜᴇ PC gamɪɴg communɪᴛy ꜰᴏʀ yᴇᴀʀs ɴᴏw… ᴊᴜsᴛ simply ᴛᴜʀɴ yᴏᴜʀ ᴀʀᴍᴏᴜʀ ᴏꜰf ᴀɴd ᴏɴ ᴀɢᴀɪɴ.
Well, unequip it and re-equip it. Redditor Thorkle13 shared the fix after saying they'd become frustrated with how squishy their character appeared to be, with damage mitigation being "nearly nonexistent even with defense mods equipped." Apparently unequipping and re-equipping the armour right before the expedition improved the damage mitigation.
The fix seems to have been corroborated by a few other redditors in the replies, though the exact cause hasn't quite been pinned down. One reply suggested that armour is currently completely broken, with the fix just causing defense mods to work again. Another reply pointed out that certain mods were breaking after cutscenes, though that could be a separate issue entirely.
It isn't the first time the old "have you tried turning it off and on again" trick has worked for Outriders, with it being the solution to a bug that was causing the HUD to disappear. Of course, the fix may not work for everybody, but it's definitely worth giving a go if you've been struggling more than usual.