I think Bloggs is onto something as well regarding decel rates. Everyone's playing by different rules when we say "adjust speed to...". It doesn't help with a million different a/c types in the mix either.
Sounds like the RTA's should be on fixes before descent then, doesn't it. You do realise that even something as small as the visual star vs the ILS star can change the fix crossing time by over a minute, and a change in runway can affect the fix crossing time by 3 minutes, don't you? I have noticed the RTA's are now getting sent out a lot earlier, but it doesn't help all that much not receiving a star until inside 60nm of the top of descent.