Murali is leading the wicket tally because he chucks it, he also happens to chuck them quite regularly at the substandard opposition of the Poms and the Jarpies.
We can only play (and beat) whoever turns up. Australia play every other top nation pretty regularly, so he has had his fair share of wins against so called "quality" opposition. I doubt he has played more than half a dozen Tests against the Bangers or the Rhodesians. I'd forgotten about the B&B, but you are probably right in saying that his effort in losing two Ashes series in a row in England will taint his record.