If I have Solosis and Duosion and Reuniclus on my bench, does Reuniclus' "Link Fusion" attack do +180 more damage (30+60+90)?
Yes, the attack does additional damage for all three of them if they are on your bench. But you do not get to add the benefit multiple times if there are multiples of the same name; for example, if you have two Solosis, you don't get to add the +30 twice.
Source: Fates Collide FAQ (2016-05-05), TPCi Rules Team (2016-05-05)