Grants resistances towards control effects.
Adjusts the duration for Weapons Malfunction and Fuse Armor. At 9 points this makes Weapons Malfunction have a 100% uptime as the duration is increased to 30 seconds.
That's 30 seconds where the target have -50% Ranged Weapon Damage and 15 seconds where it's completely disabled.
This makes Weapon Malfunction very effective in Ground STFs as you can disable an Elite Tac, Armek, Tosk or Rebecca entirely for a brief moment and drastically reduce their damage output. This helps keep people alive.
As an Engineer you really shouldn't be taking shots on the armor that often, especially with Reroute Power to Shields. There's also not that much gained, so unless you have points to spare don't fuss to much over not having Combat Armor.
Unfortunately there aren't any DOFFs which increase the damage output or reduce the cooldown, or otherwise affect the Demolitions skills. At least not directly.
Now Equipment Diagnostics in it self isn't that amazing, however with Diagnostic Engineer Duty Officers you can add a 35% chance to increase ALL Damage by up to 50 for 30 seconds. This includes damage from your Pulsewave, Orbital Strike, Chroniton Mine Barrier and Transphasic Bomb. You can slot a maximum of 3 of these.
Aside from that you can have 1 Fabrication Engineer which have a %chance to spawn 3 Support Drones at once.
Beyond that there aren't really any essential DOFFs, you could slot one of the new Tholian for increased damage against a specific enemy.
Gear & Essentials
Grab a Pulsewave for maximum damage over the least amount of shots, cone based, which ultimately resulsts in faster kills and fewer Borg Adaptions. You don't need one of the STF shop ones with [Borg], any MKXI with [Dmg]x2 and [KB3] will suffice, the damage type isn't that terribly relevant either.
Secondary I use the M.A.C.O. rifle for long range engagements on ISE and for exploit attacks.
Armor & Shields
The M.A.C.O. set is what I personally run, but you should do fine in either M.A.C.O. or the Omega set. The Omega Force set would slightly increase your Pulsewave damage at the cost of some survivability.
Beyond that always carry consumables, always without exception. You'll want stacks of Large Power Cells and Large Hypes, you don't need Shield Charges.
As for Tribbles grab the Gambling Device, as it increases your Critical Hit % chance and Critical Severity % with a 60 minute duration. Pre-buff before you go anywhere.
A note on other kit Abilities
Medical Generators heal far too little to be of any use, not to mention they are stationary which in missions that require fast clearing and constant movement is a huge detriment to their usefulness.
Turrets & Mortars deals far too little damage or fires too slowly in the case of mortars. They also can't be targeted, if there was a laser pointer type ability after fabrication their usefulness would increase immensely. However in their current state they simply aren't up to par. Mortars could also use a prediction algorithm to offset their slow fire rate, they miss targets far too often.
Shield Generators & Force Field Domes, there aren't situations where you need the protection these offers not to mention they are far too fragile in terms of Shield and HP.
In comparison to disabling the targets damage output or throwing damage at them, they lose out in usefulness again. The Force Field Dome should be a buff centered around the Engineer for the duration of it's effect, that would make it immensely more useful than a stationary object.
Shield Recharge, maybe if it was Team wide it would have some use, but in it's current state there's just about no reason to run with it. Other players have consumables or sufficient shield capacity to offset it's requirement, or simply not needed when targets die to overwhelming firepower or control effects.
Combat Supply, not even if we had this for free would I use it. Terrible beyond words. It needs a complete revamp, maybe allow players to buy consumables from it akin to an NPC merchant.
Seeker Drones needs either some different effects or a vast increase in firepower to be considered for field use. They are underwhelming in all aspects.
Go blow up some borgs! (Or Tholians, Ferengi, Klingon, Federation, ect ect)