Your description of the framing off the dock is concerning because I can’t think of a reason where joists would work as intended when installed as you describe. Their strength comes from being installed with the narrow edge used to support the decking/floor. You’re correct about updated pressure treated wood regulations. The ACQ lumber does not seem to be as hardy as the older CCA lumber. You may want to see if any dock builders supply a different grade of PT lumber? You could also use Mahogany/Ipe/Teak or any number of more exotic lumbers that stand the test of time better. I also suspect the decking failure may be connected to the joist positioning as that is a lot of surface area to have moisture trapped and it’s just as capable of damaging the underside of the decking as it is the top face of the joists. In your instance, the application of the joist tape may actually trap more moisture and hold it on the underside of the boards.

If you have a deck that may be covered by a roof, it may not be needed. It’s really only the last 15(?) years or so that’s it’s been more commonly used. The joist tape is used to protect the top face of the joist and employs a self sealing bituminous strip to seal around the fasteners and help keep the top of the joists from degrading too soon. It’s fairly cheap insurance, but it’s also worth noting that decks were built with pressure treated lumber for decades before this technology. I have never had a deck fail because I didn’t use it.

You can consider putting bituminous rubber strips on top before the decking goes on.