#5 - April 21, 2018, 10:01 p.m.
That looks like a tooltip bug in the "against current enemy" line--it appears to be showing your mitigation against a 120 in all the cases you're seeing here. You should indeed expect to see a number slightly higher than than the number in the first line, when targeting a -1 level enemy. The 25% you're seeing in the first line is in the right ballpark for a mail-wearer against a par enemy (subject to the exact items you have on, etc.).
As far as taking a lot of damage while questing, that could be either:
1) It's not just a tooltip bug and perhaps you are actually taking damage as though the attacker was 120. We'll have to look into that.
2) We're all used to questing in endgame gear on live, so it's a big shift to go back to questing in quest gear, where the enemies are a better match for you. Fighting 3 standard outdoor mobs at once is the sort of thing that should have a chance of killing you.