First, especially the volume envelope of Sampler One XT feels very "loose and spongy". The curves feel like not existing.As example if you make a steep curve, not much is changing at all, but at least not as you expect it.
And the control for the decay is very limited.
It would be nice to have a multi point envelope. These points you can add if you want and need them. So you can define which is the loop area for sustain and create different movement in it and you can create a hold phase as example, which is missing. Also a more snappy decay with two decay points as example, one very steep, one more flat. Together with the curves you can create very versitale envelopes, which are needed inside a good sampler.
There shoudl be also a trigger delay on the envelopes in sync or free. THis is important especially for layering (attack phase design as example)