As far as I know, there is no way to increase the land rate of this skill. About the only thing you can do is level Sting up to increase the bleed damage, but it seems to have no effect on land rate as you can still land a low level Sting on a high level player.
con is meant to resist bleed but i suspect thats more in pvp than pve
ive been hunting mobs that bleed for the past 8 lvls and about the only thing that helps resist it is higher mdef