Level 8 is basically end game, you will have plethora of options by then. Being able to grab Durance at lvl 2 with already 3 mechanics is much more useful especially when Aloth is pretty garbage without slicken.
Have you not gone down into the Endless Paths? I had to stop at level 8(?) for a locked door I couldn't open (mechanics 10), and the levels above that had traps I couldn't disarm...with a custom adventurer with a mechanics bump from background. Granted my party is still level 5, but having a good mechanic is pretty important as you go deeper.
As for slicken on Aloth... well, you do get spell choices on level up. There are a couple spellbooks in your path with good level 2 spells, so it isn't like you'll miss out by spending a pick on one of the best spells in the game.
I haven't gone down into the Endless Paths yet.
Given that none of the available companions is a perfect choice to be a lock picker and trap dectector. I was suprised that Obisdian didn't make one of the companions a rogue.
Would I be better off starting over and rebuilding my fighter to have more mechanics or should I hire a rogue and be done with it?