Two , the magic damage really adds up now because of OSRS gold your armour. (A way around this last aspect is to wear Hybrid equipment, like the Warpriest of Armadyl equipment, which is available as a drop from Aviansies or other creatures in the GWD) Then, you must definitely get the Royal C'bow. Ammo can be found for a very low price, is just under 1M in cost to make, and it is more powerful than CCB.
One last thing to remember: Make use of abilities as often as you can. When I cast Fire Surge on a glacor, and I apply a magic spell I do not make use of to make use of any arrows. Same with arrows in range. For slayer tasks, you'd want to avoid ultimates, and focus on basics and thresholds, until you can use Guthix' Blessing to heal, or Berserk/Metamorphosis for some crazy damage.
Well I just explained almost everything there is to know regarding the EOC and the EOC to. Maybe I'll create an explanation of this. And if you need any additional assistance, contact me here, or use the your game "Renegaderp".
If you're unable to find a royal crossbow, take you thought of buying the Armadyl crossbow. Always use 2H or dual weaponry to slay tasks. Pick the best weapon you own. If you have a level 80 ranged wep , and an 80-lvl melee weapon as your most powerful weapons choose the weapon that the monster is weakest too (according to the combat triangle).
There is no need for anything other than bandos or barrows for slaying tasks. If you do need any weapons at lvl 80 I believe it is better to get chaotic weapons and then spend the money on other items. I would suggest that players be able to only purchase the lv 90 stuff if they've got cash to buy OSRS GP burn. Your choice is yours.