A relatively straightforward awards redemption (that regularly has award seats) of SYD-MEL in Economy costs 8000 points + ~$45 taxes or ~$145 in cash. So your lowest value point conversion is 8000 points for $100, or 1.25 cents per point.
This means that 0.5 points per dollar has a minimal value of 0.5 * 1.25 = 0.625 cents per dollar (i.e. a 0.625% return). This means that at a cost of 0.95% per dollar, you are losing money.
Now, your returns are obviously a lot better if you save up for a Business classic reward. You can do the math yourself in the same way I did the Economy example, but bear in mind that it's much harder to secure Business rewards seats, especially internationally. Additionally, you need a lot more points.
To break even on your service fees, you need to redeem points at a value of 1.9 cents per dollar (0.5 * 1.9 = 0.95). So, if you think you can redeem your points at this value, then it isn't a bad idea to use payall.
I will lean towards agreeing with
@encryptededdy though - 0.5 points per dollar on a 0.95% surcharge is not worth it overall, IMO.