I looked at Goshee's guide to crew skills but it is 1.2 so what are the best crew skills for an Assassin to have?
Is Biochem still the ultimate or is Artifice just as good?
Personal opinion here, but if you plan on tanking, you should be Biochem. ALL tanks should be Biochem.
Why, you ask? Rakata Fortitude Stim. Rakata <mainstat> Stim. Rakata Absorb Adrenal (worth about 10% DR on Assassin), Rakata Attack Adrenal (less useful for Sin due to self-healing nerf whilst it is active, still great for burst damage). Zero cost to permanently incorporate another 46 points into your mitigation pool, and significantly lower cost to create Exotech Fortitude stims as opposed to buying on the open market.
Side bonus of being able to craft implants (useful for leveling alts, plus RE'ing 26+ implants).
If you're going to be DPS primarily, then it matters far less.
For a main character Assassin, I'd say general order of utility:
Honestly, for any "main", Biochem or Cybertech are the best crew skills because they provide reusable consumables.
Cybertech also is very useful due to ability to craft grenades (amazing for PVP right now due to broken resolve, though balanced by long CD), armorings, mods, and earpieces. 26+ armorings/mods/earpieces can be RE'd into molecular stabilizers (the most broadly valuable item in the game right now), in addition to the chance of learning the schematics (which can be a valuable source of income to then craft).
Artifice is a good thing to have on at least one character, and is somewhat more useful to have on a main due to the lack of legacy-bound orange saber hilts. Same basic deal as Cybertech for 26+ enhancements instead of mods/armorings, plus also hilts.
Armstech is less useful since Sin doesn't use barrels, and since legacy-bound bowcasters exist to transfer barrels to alts (though many people didn't have the foresight to nab any).
Synthweaving and Armormech are not useful for anything except augs and aug kits right now (though they can RE shells containing 26+ armorings for stabs, which is better than nothing but less efficient than Cybertech), and should be relegated to craft alts who are not actively used for PVP or PVE if at all possible.