If you can't get a royal crossbow, have a RS gold think about obtaining the Armadyl crossbow. Always use 2H or double weaponry for slayer tasks. Proceed with the highest tier weapon you've got. If you got a lv 80 ranged wep along with a lvl 80 melee weapon because your highest tier firearms, use the weapon that the monster is weakest too (based on combat triangle). You'll never need anything more than bandos/ barrows to get slayer tasks. Should you want any lvl 80 weapons, I think its better to get chaotic weapons and conserve your cash on anything else. I think people should only pick the lv 90 stuff if they have cash to burn. Up to you .

Bombardment works also in the event that you have monsters near each other and also have spare adrenaline.

2h Magic: bicycle through basics Dragon breath, string (ONLY if targeting numerous monsters, it's only semi-effective as a basic against one goal ) Combust, Sonic Wave, Impact, Wrack, then alternate thresholds Wild Magic and Asphyxiate. Double Fold Magic: precise same as above but swap Sonic Wave for Concentrated blast. I hardly if ever use 2h Melee so dunmuch there.

A few helpful hints: If you utilize Fragmentation shot right before Snapshot the harm per second is unbelievable. If you use Bombardment before Tight Bindings you get a very nice damage pile. If you've Sacrifice use it as often as possible, try and get the ones KO's using it for big heal. Berserk works too for Melee but isn't that good for Slayer considering it only lasts for 20 minutes. Additionally ask some PK'ers they actually know what is up with battle and I've probably left out a lot.

Really wish I could provide a cheap OSRS gold good answer to this issue but I haven't done the research since the battle improvements update which changed many skills. The problem is that Jagex has really, really terrible communication between their authors and code guys, and both website and ingame descriptions tend to be completely false compared to the real code. A good instance of that is Wild Magic pre combat enhancements: its own ingame and website description states that it must do between 25 percent and 250% damage, while in fact it did 73%-219% damage. There were many other mislabeled skills pre combat improvements.