For most (possibly all?) game modes, the loadout used is saved from one to the next. However, because gauntlet does not allow reuse of heroes, each tier is a blank slate (except tier 1 uses the loadout of tier 5 from the previous day). The issue here is that the heroes one faces up against, and the corresponding loadout you use for each tier, tends to be similar from one day to the next and you’d like to use the same loudout as the previous day but are met with a blank loadout instead.
The current workaround I (and possibly others) use is to screenshot the loadouts and swap inbetween apps to ensure I build the same teams each day. This seems quite clunky and it seems like a more frictionless solution would be to implement auto-saving for gauntlet at the tier level.