I believe that guide focuses on crew skill synergy including Efficiency ratings which I don't have an opinion on efficiency's usefulness. You should never have to have more than two of the same crafting skills except for maybe Biochem and Cybertech for their reusables if you wish to do so.
Now on the basis of which class gets a crit in a crafting skill then (I got this from psandak's post that summarizes them)
Synthweaving: Knight/Warrior (+5 crit)
Biochem: Knight (+5)
Armormech: Trooper (+5)
Armstech: Smuggler (+5)
Cybertech: Droid sensoring unit (+5)
Artifice: only treek and HK (+1)
These are the absolute best crits for each crew skill of those classes. I don't remember the classes that have craft crits that aren't (+5) like (+2 crits).
For missions skill crits:
Diplomacy: IA (+5)
Treasure hunting: Warrior (+5)
UT: IA and Inquistor (+2)
Investigation: Smuggler and Warror?(+2)
For slicing: Knights, Inquistor, IA, (+2 crit), Smuggler (+1)
Again these are just the "best" or highest and some class will have crits in those areas like trooper and Consular both UT (+1) and Dipolmacy (+2)
For "best" synergy in terms of crits not including efficiency :
Trooper: armormech
Smuggler: armstech
These two just practically seem to be made with those craft skills in mind
Cybertech: (need droid sensor unit for Crit) Trooper (crits in UT and scavenging), can also do consular (crits in scavenging and UT)
Not as important synergy:
Artifice: SI (Archeology crit +5 ) or SW for TH (+5) (also SI gets +15 artifice efficiency if you care) HK and treek needed for Artifice crit
Biochem: knight (high crit +5) or BH (bioanalysis crit +2)
I might miss some other classes but those are the synergies off the top of my head.
Also if you plan to do many alts then just the craft crits matter since all other alts should be pure gatherers/craft supplementers. and can supply material for your crafters. Lastly crits don't matter as much (still beneficial though for costs vs gains) in gathering as in missions or crafting as it gives more of the same thing within that rank.
It seems Pub heavy so if you don't want that then for IMPS:
BH:Biochem/armstech
IA:armormech
SW:synthweave
SI:zero believe or not (+15 artifice efficiency which is extremely high)
I'm not an expert on crafting bonus perferences and whether or not +2 vs +5 crit is a big difference.
Psandak might chime in and help on this topic.