airfoilmod
If you read my post properly, I never said that a aingle engine failure in a twin should not be a MAYDAY. I was replying to (and disagreeing with) Old Fella who inferred that a single engine failure in a twin was the same as flying in a single engine aircraft!!
As for a seperate frequency for the Mayday aircraft, not always the best option (and is not a general rule for ATC to do, as you allude to) - each case needs to be looked at in isolation. If the frequency is busy, then yes a good idea, if it is only moderately busy, the drawbacks of having two controllers working aircraft on different frequencies in one piece of airspace often outweighs the advantages.