So, have levelled and nearly / have finished Nightmare and a bit of Hell w/ both a Wizard and a DH, will throw my experience out there.

For Hatred generation, it'd entirely depend on the scenario. Typically I'd use the ability that knocked you back, Evasive Shot, however Chain Gang with the 4 man snare was extremely helpful on occasion to protect Wizard buddy.

For Hatrid dumping, again situational. Frequently Rapid Fire, occasionally the Impale w/ Overpenetration or Impact, otherwise Razor Disk Chakram. Damage wise out of the three, Rapid Fire for single-target or Impact with the bleed ( Chemical Burn ), Razor Disk Chakram for repeated AoE, and Impale w/ Overpenetration for line-based AoE ( think corridors ).

Then for action slots, Caltrops ( the trap ) with Hooked Spines without a doubt, 80% slow is incredible. Smokescreen with Displacement, an absolutely incredible ability for escaping wallers and the likes ( threat dumps ), and then two situational abilities again. Vault ( any rune really, none spring to mind as particularly better than the rest ), Marked for Death w/ Contagion for large AoE packs, Spike Traps for corridors where you know a large mob will be walking through, and Sentry.

Onto tips, Dexterity is great but it needs to be stressed that Weapon Damage ( and Attack Speed ) outperforms it by such a great scale, far from 1:1. 3-6 Weapon Damage will probably trump 30 Dexterity, check your Stat Changes when Equipped ( hit Alt to compare against your alternate ring equipped ) if unsure.

Strive to never get hit by melee attacks, you only become squisher and the enemies only become soakier with each difficulty and act increase, get the hang of kiting ( attacking whilst running back efficiently ) using Chain Gang if need be, albeit your traps should be sufficient.

If you're with a friend, a particularly squishy one too, consider running Multishot w/ Suppression Fire so you can use your Hatred to gain more Discipline for further traps and the likes, they do go a long way.

Chakrams with Razor Disk, fire them just a bit ahead of your target, confirming they'll slice through your enemy, whilst I suggest you try them, I've found grenades in general to be mediocre at best. Bola Shot isn't terrible, the explosion effect does stack ( you can shoot 4x in 1 second and a second later there'll be four explosions ) so it is rather good for high HP mobs, and Evasive Shot is extremely good because not only does it deal very impressive single-target damage ( using Shrapnel ) whilst generating Hatred, it has no travel time unlike every other projectile of yours, making it great for long-range fast moving mobs.

If you've any questions about the class, unsure about specific abilities, I'll happily lend a hand.