Solanium and crit chance will only be required if you run with WD dps because of their Gruesome Feast passive. You can drop both if you have other dps classes.
Supp DH is extremely tanky, so you can drop all defense in favor of better stats.
I strongly suggest watching the video or some of my group clears to see how it is played. Supp DH requires a lot of practice to execute properly, as every monster type has different behavior when you pull them. Supp DH generally replaces supp Barb in groups.
You have to move around constantly to keep monsters engaged, DH is a very active role. Be aware of your surroundings, guide the party to good spots and then try to pull monsters from all directions while still keeping up your buffs. Sometimes you have to go very far or spend a lot of time on pulling elites, so try to vault in and out with an occasional Multishot while still spamming your generator to replenish discipline.
Engage monsters and lure them back to the rest of the group with grenades + taunt effect from Boyarsky's Chip. As long as you are close enough, try to Multishot once every 3sec to keep up Iceblink and the crit buff, and also try to proc a globe from Solanium once in a while. Put Marked for Death on a low hp target once you engage new monsters and spread out some sentries so you cover a big area, your party will have to move around a little for Oculus procs. You have Nemesis Bracers, so it is your job to click pylons and bring elites to the fight.
D3planner link: http://www.d3planner.com/919034671
(2.4.1) 124 4man clear: https://www.youtube.com/watch?v=A0uZVFi_O-Y
(2.4.1) 125 3man clear: https://www.youtube.com/watch?v=loDsnHvDe40