If you've got Sacrifice you should take advantage of it as much as possible, try and score those KO's for big heal. Use Sunshine as well as Death's Swiftness whenever you can. Berserk can also be OSRS Buy Gold used for Melee however it's not a great choice for Slayer given that it only lasts for 20 seconds. If you ask PK'ers, they're very knowledgeable when it comes to combat and i've likely left a lot out.
I'd love to have a good answer to this query, but I've not done any research since the combat improvements update which changed the capabilities of many. The issue has to do with the fact that Jagex has really really bad communication between their coders and their writers, while both their in-game and site descriptions often are completely false compared to the actual code.
A good example is Wild Magic pre combat enhancements In-game and on the website description states that it will be able to do between 25 and 250% damage, but in reality, it only did 73% to 29 percent damage. There were several other abilities labeled incorrectly prior to combat improvement. A lot of abilities are being labeled incorrectly, but I don't have any information on them.
The other thing that I'd like to know is the proper recharge time for abilities. Jagex has an extremely irritating insistent on using seconds, with a wildly inaccurate rounding, instead of making use of decimal values or saying "game ticks". Also, you really should not ask pkers questions about DPS since it is not a factor in Pking. It's about stuns and defensives, prayer disruptions and high burst damage combos. If you attempt to hit someone with a standard pvm strategy they'll tank you for many days.
I purchased The Spider Orb from the Grand Exchange and put it to use to fight under the Barbarian Village. First thing I observed was that the animation seems to suggest the spell is emanating from it's Spider Orb (And not the Spider Wand, which I also have equipped).
On the Runescape Wiki, I read the following about Spider Orb: Spider Orb: "The Spider orb is a magic object used in the slot for shields. It requires 20 Magic to be worn. It's the off-hand counterpart to Cheap RuneScape 2007 Gold the spider's wand, and it allows players to use spells from the off-hand slot."