It wasn't me who updated Wikipedia but I do update a spreadsheet for my own amusement. Until very recently, Blackwell was second only to Spackman in the points per game rankings. He's now slipped to joint third.
I would say you can't compare his record this way with the likes of Warnock, Bassett and Harris who all had spells in the top division but it's a fair comparison with Spackman, Kendall, Bruce, Robson and Heath who only ever managed us in the second tier. On that basis, he was doing very well but is gradually slipping as the resources drain away.
Rank Manager P W D PTS AVG Win %
1 Spackman 43 20 17 77 1.79 47%
2 Kendall 82 34 27 129 1.57 41%
3 Blackwell 118 50 34 184 1.56 42%
4 Porterfield 226 98 58 352 1.56 43%
5 Warnock 388 165 100 595 1.53 43%
6 Harris 612 258 144 918 1.50 42%
7 Davison 592 248 139 883 1.49 42%
8 Mercer 154 64 35 227 1.47 42%
9 Bruce 55 22 15 81 1.47 40%
10 Freeman 132 54 30 192 1.45 41%
11 Nicholson 1216 486 281 1739 1.43 40%
12 Robson 38 14 12 54 1.42 37%
13 Bassett 393 150 101 551 1.40 38%
14 Coldwell 23 9 5 32 1.39 39%
15 Rowley 43 16 11 59 1.37 37%
16 Furphy 80 27 22 103 1.29 34%
17 Thompson 17 5 6 21 1.24 29%
18 Mcewan 86 27 25 106 1.23 31%
19 Haslam 158 50 40 190 1.20 32%
20 Heath 22 7 5 26 1.18 32%
21 Sirrell 81 20 23 83 1.02 25%
22 Peters 16 3 6 15 0.94 19%