Engineering is a profession with widely varying profitability. In The War Within it is not the worst for concentration, so let’s look at what you can do with your concentration.
Embellishments and potion bombs
There are two main options for using your concentration with engineering in the embellishments and the Potion Bomb of Power. Currently I’m looking at 8-10 gold per concentration for these two recipe types, which is on par with most professions outside the top two.
The best embellishment
For the embellishments I would suggest doing Pouch of Pocket Grenades or Energy Redistribution Beacon as they have much higher sale rates than the Concealed Chaos Module. The embellishments I’ve crafted have sold quite well.
The build
My build is all over the place and I still have a lot of skill for the relevant crafts. The most important part is to max out the base node in the inventing tree. With that and high skill you can reach concentration thresholds for pretty much everything. You can then go for more skill in Devices or the resourcefulness and ingenuity buffs in Inventing. The ingenuity tree can get you a 12 hour buff when you invent with significant stat boosts, and is quite good for that reason.
Multicraft, always multicraft
Multicraft is as always the top dog stat. Make sure you get that on your profession tool, and upgrade the helmet to rare quality before the gloves as the helmet has multicraft. Ingenuity is likely second best for a concentration build, but resourcefulness can be good as the embellishments have some expensive materials on the material list.