Those stats clearly show that both bowlers have increased their workload in recent times which suggests that Australia are taking longer to bowl sides out. Warne has improved his strike-rate in recent times compared to McGrath but that is not due to less overs bowled by McGrath. Warne's workload has only marginally increased but his wicket-taking ability has increased dramatically. McGrath's SR in his last 10 matches is 46.07 compared to 49.7 from the previous 10 matches which is an improvement so it's wrong to suggest McGrath's wicket-taking ability is waning. It appears to be marginally improving. By comparison, Warne's SR has come down from 54.48 to 40.17 - a very noticeable difference!