The idea is to stack enough weapon damage to contend with Strikers. Booster Shot Competent Alphabridge Weapon Damage Bonus Uncomplicated 12% Assault Rifle Damage on gloves = 60%-64% weapon damage, equal to 60-64 Striker stacks or half an Extended Mag from an M4.
This build shreds in Skirmish, shreds in Last Stand with smart play, and can really shock people in the DZ if you are in a competent group or not goingnow3v1.
The Bullfrog's extra RPM gives a small, added boost with stability on back pack and a stability mod to control it. You can try an accuracy mod instead to see if it works better for you. The wild bullet come of the Bullfrog is the real issue once you get past 20% stability. This build still has 18-30% crit chance and 98-123% crit damage thanks to crit chance on gun and gear and the talent Precision. If you can control the Bullfrog with 3 crit damage mods (with stability as minor attribute on all of them) instead and just stability on backpack you will hit a bit harder. If you feel brave you can replace health on knee pads and stability on backpack with crit damage to really hit harder.
When facing someone heads up use booster shot. The skill haste will have it back in 35 seconds. When the Booster Shot/Competent stack runs out you can drop the immunizer to refresh the stack or blow it up for burst heal. By the time Booster Shot is back you'll almost have immunizer. Immunizer comes back I'm 28-30 seconds. You should be able to have competent actice for most of an encounter.
The only sustain heal is in the health regeneration and Predatory on the sidearm. If you can stand in a support station for 4-5 seconds without taking damage, or if you can proc Predatory with your sidearm (finishing a downed agent, destroying a turret or support station) and not take damage for 4-5 seconds, your health bar will refill really really fast. Situational but the opportunity arises more than you think.
The signature skills proc on downs AND kills. With a 7FA - 6 STA distribution of main stats you'll have the signature skills for 6 seconds, more than enough time! When Survivor Link activates you will have over 1 million toughness thanks to On The Move. When this happens you must pop Booster Shot to raise your toughness even higher and go on the offensive. If your health is real low just use the burst of speed to flank or seek safety to heal. When Tac-Link activates go on the offensive, switch weapons if you have to. When Recovery Link activates seek some cover to let it over heal you or get you to full health at least. When you are lucky enough to stack signature skills kill with extreme prejudice.
If you want to go 5 piece instead in order to share Sig's with the group, I'd recommend a Rapid chest for a skill haste boost.