Showing balances across multiple mints, each potentially having multiple assets does sound challenging. Maybe you could allow toggling between one view that is ordered by mint and then by asset within the mint, and a second view that is just an aggregated total across all mints for each asset?
Discussion
In the second view when the user taps on a line showing the multi-mint total for a particular asset, an accordion could expand underneath showing the per-mint totals for that asset.