I've been playing since like 2004. I know a decent amount about staking. Defence pures do own, i owned a range tank that i used to stake with (80 def, 96 range). I owned a 1 def pure (60 att, 85 str, 1 prayer), it went okay. A berserker pure (80 att, 96 str, 45 def, 52 prayer), it didn't do too good.
The problem with defence pures though, is because they are so good, no one wants to fight them. The trick is to stay off the radar. You can have like 60 att, 60 str, 60 def, 1 prayer, and none of your stats will show up in highscores. So use those sort of things to your advantage.
I'm contemplating making another defence pure, don't know if i can be bothered though.