It's hard to say because the 1.6 patch notes are not final yet, but for pve content the following sets look to remain strong:
D3-FNC
Reclaimer
Tactician
Striker
Specialized will be less effective come 1.6 so might not be the best option.
Relentless works way better for skill builds as you can invest purely into SP and get healing from offensive skills, no need to run heal as a skill and focus purely on damage dealing skills.
Resourceful is also more beneficial for 1.6 as any healing will heal your skill objects (shield, turret) with the nerf to shields and turret health.
For example, this is my skill build in 1.5 and it kills everything in 2 seconds.
3 tac + 3 firecrst in the pic but I usually run with 2 Tac, 3 Firecrest + Relentless backpack (for the healing). Running seeker mines + flame turret, switch to sticky bomb for single target damage. Using 4 AOE talents: wildfire, demolition, shrapnel and chain reaction.
Sticky bomb does over 1 million damage (even a m44/carbon sniper can't hit that high) and you can one-shot named bossed when Technical procs.
I NEVER HAVE TO FIRE MY WEAPONS lol
Predator 4 piece was average when it came out will be worse off with 1.6, so not advisable to spec in Predator's, especially not for pve.
To get the most out of the 4 set, you need a weapon with high base damage since that determines the damage of the bleed, so SMG's for a Predators build is the worst thing you could do, since SMG"s have lower base dmg numbers than AR's and LMG's.
3 predator combined with 3 striker is pretty strong though.
That was last week, vendors reset 20 hours ago and this week's roll is bad.