in the first innings of the 1018 T20I's played since 2005, the average balls faced by number 7 in an innings is 7.2 balls. This figure is total balls divided by total matches. If you change it to total balls divided by total innings, so removing the 10% of matches where the number 7 wasn't required to bat at all, they face 8.6
in the second innings of the 1008 T20I's played since 2005, the average balls faced by number 7 in an innings is 6.4 balls. This figure is total balls divided by total matches. If you change it to total balls divided by total innings, so removing the 35% of matches where the number 7 wasn't required to bat at all, they face 9.7 balls
there's no great way to measure how often the 6th bowler is called upon (because sometimes they're used at the top, etc) but in the first 10 games of last season's BBL, again in the first innings (to exclude early finishes, etc), 8 of 10 innings used 6 bowlers. Of those two, one was reduced to 19 overs (Heat the bowling team) and the other one was the only case of a team being bowled out (Scorchers). Often two bowlers bowled 2 overs to make up the 4, sometimes it's just one over.
So the 6th bowler basically bowls 6 to 12 balls. And the 6th batsman faces 6 to 12 balls.
last night's teams both had keepers who legitimately deserve a place in their top 5. last night's teams did not have bowling options in their top 5. (sorry Renshaw, this might change). this means each team basically had a "extra" spot in their team because they don't need to cram in a keeper at 7, but they only had the strict 5 bowling options. therefore they used the extra spot to pick the 6th bowling option. in the case of the Thunder, 3 of their bowling options can bat a bit (Sams, Green, Nair). In Brisbane's case, it was Cutting and Steketee (and Steketee Can Bat - he's got FC 50's, has cleared the fence a fair few times and didn't embarrass himself last night). I think Steketee at 7 is fine given they don't have an all-rounder to fit in. So would you rather Steketee face 6 balls or Renshaw bowl 1 or 2 overs. It's much the same imo. I think the much bigger Steketee problem was that he bowled out while Swepson bowled only 2. And of course the much much bigger problem was that Brisbane's top 5 flamed out