I've been using this build as my goto standoff PvE build because it's pretty low maintenance (non-traditional) ranged build.
Why run an Inventive backpack build instead of 6 piece Tactician? Since they changed the way you are able to build stacks, a seeker/sticky build will waste more time building stacks than actually dealing damage. You will sacrifice DPS for a larger initial hit. It's not as impressive, but flat out :you will deal more damage.
"I see what you didn't run a 6 piece, but why not run at least a 5 piece build?" You only gain a 5% increase to your skill haste and skill power by doing this, and the advantages of barrett's chestpiece (10% skill power with 0 skills on cooldown, 5% damage with 1, 10% armor with both) far outweigh that 5% (even taking into account that initial skill power bonus only applies to the first seeker, the subsequent 5% damage bonus would still remain in effect for most of the fight since you are alternating between skills).
The math: Barrett's 10% skill power, Inventive 15% skill power, single stack (30%) = possible 55% increase in Skill power. 6 piece Tactician: 5% with a double stack (60%)= 65% possible. A 10% reduction, but the time building stacks in between using skills is far too high to be effective in a fight.
Note: Make sure you have the lightweight M4 equipped when using the explosive skills, it will add 10% damage.
Tactics: Begin with taking cover, sending out your seekers to get the bleed damage started. Once the seekers are out, line up a group to sticky bomb to maximize the amount of damage you can do with a single sticky. Detonate the sticky AFTER the seekers detonate. Get back behind cover. By the time you detonate your sticky bomb, your seeker should almost be refreshed. Rinse and repeat. The bleed damage will usually take care the lower constitution enemies, leaving you with the heavies to deal with a sticky bomb.
This simple build is great fire support in a well rounded party or a great solo build for the cautious. This build is even devastating in the underground against agents, but you will have to be very cautious since you will be disrupted if they get too close or caught off guard. This one works well for me but this isn't the most optimized of equipment, you can tweak things to better suit your play style.