Re: Boss destroying skill
yes you can revive merc in hardcore. And your option are good, though I'd go for estone.
Why?
Removing non-merc relevent skills they come out at:
Stone
+60% Faster Hit Recovery
+300 Defense Vs. Missile
+16 To Strength
+16 To Vitality
+15 to all Resistances
~4000 Defence
Treachery
+45% Increased Attack Speed
+20% Faster Hit Recovery
+30% Cold Resist
+60% to all Resistances
+Almost No Curses
+15% Damage Reduction (does this apply to mercs, or is it just assassin hard points?)
+300 Fast Poison Damage/hit
~1000 Defence
(Assuming fade and venom have been activated, but considering how much a merc gets slapped around it's fair to say they're almost always on, and assuming you make them in a ebugged elite armor.).
I don't know - the only advantage of Stone seems to be more defence and 40% higher FHR, but unless you're going Defiance I'm not sure that the defence will do you all that much good. And it won't help at all vs casters.
Aside from the defence and FHR, I think Treachery beats out Stone pretty easily - you get massive IAS (watch that turbo charged Jab with Obedience Crushing Blow + awesome damage), Great Resists (there are very very few armors that beat 60% Resist All), Nice DR, Curses last only a few seconds and a nice source of poison damage. And it's much cheaper. And your merc looks cool.
To me the only drawback is the venom which means you either learn to live with poison only being active for about half the battle due to the short duration or you get a source of open wounds. Either way - I reckon the damage output from the faster attacking and fairly high poison damage will outweigh the PMH effect of a longer duration poison.
I just really like Treachery - It's cheap, it's cheerful, it's awesome. It's been my standard Merc armor since the moment it came out. It's rare that I use anything else unless I'm going for a special effect.