Scrapper or Conditions for high fractals?
I’d say conditions primarily because higher level fractal mobs have increased toughness and for the few things that Scrapper utility could be useful for, you can simply switch tools to scrapper without too much of a DPS loss.
That said Power Scrapper is still viable.
Now you don’t need toughness / inventions / alchemy, what you want to do, is to keep mobs blinded with mortar 4, bomb 4, grenade 3, ft 5, and pistol 3. Time your blinds and you should have no problem. In the cliffside fractal during the hard seals event, I am able to chain pull tank one side because of exactly that.
Engineers have a lot of different tools at their disposal for soloing most things. I, as well as others, have soloed Hearts and Minds migraine mode with an engineer. It takes a little ingenuity and practice, but it’s very possible.
Go for the condition build.
It does a lot more dmg indeed, and you can replace the Inventions line by any other line you whish. This means, you can go for scrapper as well, choose the sneak gyro, and the bullwark instead of the the flamethrower.
And if you need the perma stability – just go for it in the condition build as well. You will lose some dmg, but it will still be a way higher dmg than the power build.