OK, a few thoughts:
1, 5-an-over is too expensive at any time. Any full-time bowler should be disappointed to have gone for 5-an-over in any one-day game. To accept 5-an-over, for me, is an acceptance of mediocrity.
2, no, you can't just judge bowlers on statistics, but an economy-rate for 5 overs or more is usually a fair reflection of how accurate someone has bowled. For me, I only ever give credit for wickets that have been taken with what I would call good deliveries.
3, bowling has always to be taken in context. Anything over 4-an-over in what I'd call favourable conditions is too expensive (eg seamers in typical English, Kiwi conditions or fingerspinners in typical Sri Lankan). 4.4-an-over is perfectly acceptible for someone bowling in typically unfavourable conditions (eg fingerspinners in England). For someone regularly bowling in the last 10 overs, an extra 0.1-an-over is added to the acceptible and good.
4, yes, the one-day game in the 70s and 80s is not far from incomparable to that of '92 onwards. But Garner's record would still probably be about 3.7-an-over if he bowled today if you ask me.
5, James Kirtley is not a good one-day bowler IMO. He has played ODIs for a long while now, I never thought he should have been selected in the first place as his List-A economy-rate is over 4.6-an-over. And his ODI record is dreadful, no two ways about that.
6, Waqar Younis is nowhere near the one-day bowler he used to be. Since he took the Pakistan captaincy his accuracy has just gone to pot. Take a look at his county record last season. An international bowler should be going at less than 4-an-over in OD and 3-an-over in FC cricket, when he gets into domestic stuff. Waqar went at at about 0.8-an-over more than that. I was very disappointed in him.
7, Simon Jones' one-day credentials are, for me, summed-up by the fact of 5 one-day games in 5 seasons at the club (excluding 2003, as he didn't play First-Team cricket), and the record that accompanies it. I don't think he'll ever be a good one-day bowler, but eventually he'll play another one-day game and we'll see if anything has changed from 4 years ago (the last time he played a List-A one-day game).