OK - I'll exclude the Wing Derringer and Diamond TwinStar from my 'avoid' list!
In something like a typical commercial FTO operated Seneca, flying an approach at the correct POH approach speed and configuration is there:
1. Any modification in IAS or configuration applied when asymmetric?
2. Any additional height loss in the event of an asymmetric go-around when compared to a go-around with both engines operating?
If the answer to 2. is "Yes", then whatever that value is should be added to the normal DA.