Hey Chuck, welcome, I was wondering when you’d start posting here. 
One of my alts is a dual-pistol sorceress, which should work with a rifle as well. I prefer the rapid fire rate = more/faster devotion procs, but I can see the value of a rifle in kiting situations. If you only have a moment to stop and fire, better make that shot count… The build I’m following is mad_lee’s People’s Gunslinger.
Another possibility would be to go pyromancer (occultist, used just for a handful of great support skills) and focus on chaos damage. A quick look at Build Compendium V turned up JoV’s tanky 2H ranged build.
A general point about builds in this game - one should focus on one, maybe two damage types, and pile on as much resist reduction as you possibly can to support it. RR is not “nice to have” (as I initially thought), it’s essential. So a fire strike demolitionist-based character almost certainly needs Thermite Mine (and Hellfire Mine if going chaos). Unless you go physical damage and use Soldier. If you haven’t seen it yet, the debuff cheat sheet google doc is extremely helpful to understand what different wordings of RR do and do not stack.
Another “we’re not on Pandora anymore” realization was that percent damage in this game isn’t nearly as awesome as it looks. If you look at page 2 of your character sheet, you’ll see your Physical Modifier, Pierce Modifier, Fire Modifier, Chaos Modifier, etc. for all different damage types. And the one(s) you focus on will be in the few-hundred percent range pretty quickly. So if your thinking is “Searing Might = +18% damage for 3 skill points, great!”, eh, it’s something but it’s not actually very much (maybe it’ll take you from 500% damage modifier at level 50 to 518% damage modifier). The crit damage from Searing Might is decent though.
And for planning things out in grimtools, FYI there are a lot of endgame items that give +skills so you generally won’t need to spend 12 skill points to get a skill to 12/12, if that’s where you want it to end up (Explosive Strike, for example). Also, grimtools is based on the AoM cap of 100, so we have to leave those last 20 skill points and 5 devotion points unspent (unless you figure you’ll pick up AoM before your characters hit 85).
Apologies if you already knew most of this! 