Yeah its pretty huge nerf to toxic rain(and explosive arrow being collateral damage). You could still maybe make it work with a +3 bow but yeah, as a starter it's kind bad now.
If Arc doesn't get gutted in the notes still leaning to Arc totems for a starter, played the shit out of minion builds in Delve so might want a break from that.
Yep, you want to pick up increased duration and AOE nodes from the tree. Basically it's a DoT build, the snare effect is also really nice for keeping shit off you(though looks like slow effects are getting a cap).