Health is a devolved issue.
Yes, it is now. And before it was a devolved issue, much of it was overseen by the Scottish Office.
NICE in England was only set up in 1999. Before that decisions were made at a Health Board level.
My point is that some things blamed on devolution aren't the fault of devolution.
Your substantive point that asymetric devolution throws up problems is of course correct. My MP was until the reshuffle a junior minister for a function that was devolved. Therefore if I wanted to pursue that with my elected representative, I'd have had to contact my MSP and/or the relevant Scottish Minster.
The current Prime Minister cannot make decisions about health, education, agriculture, fisheries and forestry, economic development, environment, food standards, home affairs, police and fire services, sport and the arts, transport, and so on in his own constituency: for all that he has to write to his MSP. But he can make decisions on those things for England.
Scottish MPs abstaining from votes on those matters wouldn't really help: do Welsh MPs abtain on the different list of matters devolved to the Welsh Assembly? Northern Irish MPs on the different list devolved there? Do London MPs abstain on the yet again different list of matters devolved to the Mayor and Assembly?
A bit of a mess.
Either there should be a Federal UK, or the constituent countries should be independent. Westminster in its current form isn't really sustainable.