Yes, it is more likely that a single <connection-definition> per <resource-adapter> will suite your case better.
Some background on why IronJacamar 2.0 - connection definitions can have a ResourceAdapter instance associated, so in order to support adding or removing connection-definition from a specific deployment we need to do a lot more tracking of the resource adapter object that IronJacamar creates during deployment. That isn't possible in IronJacamar 1.x.
Hence 1 <connection-definition> (or 1 <admin-object>) per deployment is better atm.