Just at a glance, it seems like the latest version of Decker will meaningfully reduce the size of the deck, and thus improve loading time. (Don't forget to update all the modules you're using along with Decker itself!)
I have some theories about incidental performance overhead caused by the large number of cards in this deck that I might be able to fix- or at least improve- in the next Decker release; I'll investigate.
EDIT: I've identified and addressed an internal bottleneck; having 500+ cards was causing event dispatch to take longer than usual, exacerbated by the fact that Dialogizer emits animate[] events at 60hz. Decker now handles binding local card and widget names for event scripts more efficiently. I think this tweak should significantly improve the performance of your deck in both web- and native-Decker. These improvements are available now if you build Decker from source and will be included in the v1.66 release, probably available on Friday.