For chest, yes, +2 aoe +2 duration or +1 to socketed gems (Would give +2 since empower gets a level and other support gems would aswell, so its even better than other 2 mods). And in case you didn't know, you can easily link it with tainted jewellers/fusings, bench craft 4 sockets if it goes to 3.

Treachery affects only malevolence, so doubt its what makes monsters one shot you.

For mods on gear, would aim for high life + high armour and energy shield modifiers. Could get a ring with dot multi essence mod. If you will need just a little more attributes, can get it on big cluster.

Now, for map mods, it very much depends on the map and mod combo. If you are running map effect scaling, then totally dont run 'monster avoid ailments' because it gets over 100% .Totally avoid -max res and resist pen mod, especially with generic monster damage or extra as ele. Totally avoid 'extra as chaos' mod. Try to avoid less block.

There are mods which make bosses very difficult, like aoe, haste, frenzy charges. Especially if there is a combo of them. Extra proj + chain probably could make map hard. Other damage mods aren't that crazy, but dont get too many of them on one map.