As best as I can determine- the latent effect is simply that it is used- you have to actually hit the mob. If you do, you have what seems to be around a 1/15 chance of warping.
the con of the mob is irrelevant, as is your HP, TP, moon phase, and day. When I first got it- I walked outside (as a level 56), whacked a bee. It missed me and I warped. One hit, no damage taken. It was firesday.
I think the latent is much more like the "Added effect" seen on other staves- like ice or dark. If you hit, you have some chance of the effect going off.