This does seem to be a bug with the leaper-class monsters in 1.10.
At least four times today, in two different singleplayer games, I've encountered elementally-invulnerable leapers in Act 2. Here's the information I have so far:
1. Leaper ran up to my sorceress and was frozen in mid-attack by her Frozen Armor.
2. Sorceress attempted to harm frozen leaper with Frost Nova / Ice Blast / Glacial Spike
3. Leaper appeared to take no damage. (This happens seemingly at random, sometimes producing elementally-immune leapers and sometimes not.)
4. Leaper thawed and had thin, ~1 HP life bar. Sometimes a death animation will occur, followed by the leaper magically rising up to continue the attack from earlier.
5. Hireling ignores the leaper, but the leaper can attack and damage both the hireling and the sorceress.
6. The elementally-invulnerable leaper apparently can't be frozen, chilled, poisoned or burned, though it can be killed by a physical attack by the sorceress. (So much for not getting her hands dirty.)
I'm thinking that something is bugged with the Frozen Armor freezing effect that is causing leapers to not register damage taken while frozen.
At any rate, I had it happen two more times last night and just killed the leapers with my sorceress' melee weapon (an orb). This tactic won't be a good idea in Nightmare and Hell, because my sorceress is not made for tanking, so I'll just have to find ways to park or ignore the affected leapers.
(Edit: revised findings after reading similar post on b.net open support forum and encountering a few more occurences of the bug.)
At least four times today, in two different singleplayer games, I've encountered elementally-invulnerable leapers in Act 2. Here's the information I have so far:
1. Leaper ran up to my sorceress and was frozen in mid-attack by her Frozen Armor.
2. Sorceress attempted to harm frozen leaper with Frost Nova / Ice Blast / Glacial Spike
3. Leaper appeared to take no damage. (This happens seemingly at random, sometimes producing elementally-immune leapers and sometimes not.)
4. Leaper thawed and had thin, ~1 HP life bar. Sometimes a death animation will occur, followed by the leaper magically rising up to continue the attack from earlier.
5. Hireling ignores the leaper, but the leaper can attack and damage both the hireling and the sorceress.
6. The elementally-invulnerable leaper apparently can't be frozen, chilled, poisoned or burned, though it can be killed by a physical attack by the sorceress. (So much for not getting her hands dirty.)
I'm thinking that something is bugged with the Frozen Armor freezing effect that is causing leapers to not register damage taken while frozen.
At any rate, I had it happen two more times last night and just killed the leapers with my sorceress' melee weapon (an orb). This tactic won't be a good idea in Nightmare and Hell, because my sorceress is not made for tanking, so I'll just have to find ways to park or ignore the affected leapers.
(Edit: revised findings after reading similar post on b.net open support forum and encountering a few more occurences of the bug.)