On the wiki it says the max amount of xp that can be gained per hour is 138k if you harvest from Undead Souls. Doing this can either grant you a Death Rune or Soul Rune which are worth 2.5 and 3.5 points respectively.
Assuming you do actually get 138k per hour, and you get an even amount of death and soul runes, you will get approximately 399.5 xp per 2 siphons (one death and one soul).
138,000 / 399.5 ~ 345 of each rune type.
Then if you add up the points
(345 * 2.5) + (345 * 3.5) you get approximately 2,070 points/hr.
Note this answer assumes a Runecrafting level of 99. Also, keep in mind this answer assumes you will get equal amounts of death and soul runes and that you will not fail a siphon in that hour, so YMMV when doing this.