Spiritual Chain is alright, but the three extra links on Joint Penalty can be thought of as adding three extra hits on every attack from everyone in your party. The truth is, even if Linker had no abilities except Joint Penalty, it’d still be a highly sought after class…
As a full support build, if you already went Linker1, then your only other option here is Thauma1 instead of Linker2. Thaum1 is good too, Swell Left Arm is an excellent buff; and Swell Body has utility in combination with Reincarnate if you’re planning on going Chrono.
These are my thoughts currently as a Cryo1/Linker2/Chrono
Also, everyone complaining about damage is being over-dramatic; I can still solo just fine. Archers will KS the ■■■■out of you, but who doesn’t get KSed by them anyways? Just make sure you spend money on Enhance attributes for Energy Bolt/Ice Bolt/Ice Pike or your pyro skills if you went that route. Again, your damage per hit is pretty bad, sure, but linking 8 targets is technically increasing your damage by 8x depending on what attack you’re using…