Lucines guide is great but I prefer what I did and it worked.
Elite Void with Mage + Melee helm.
Any Runic Accuracy aura.
Any Scrimshaw of Elements.
Active blood spell. Preferably barrage since burst is 79 and C staff is 80 and that 1 level makes a difference considering abilities don't use runes ever only auto attacks do.
Overload Salve. Like 4 brews and 8 super restores and 3 adrenaline pots and Excalibur.
Weapon poison++
I yolo'd it with Jagex's recommended action bar and used Meta over sunshine (Sunshine is better so use that) and got to wave 22 with alot of derps and glacors spawns woo.
23 if muspahs.
That should work for 15 too. But if I presume you haven't done 20 (technically 21) yet. You may as well hit two birds with one stone.
I know Warpriest and Slay helm apparently works during Iowerth VoS, but for me it seemed to make me hit a lot less accurately on anything that wasn't my slay task so I went with void and had no setbacks.
I Melee TDS (when it prays magic) and Airuts. I never zerk. I use 2h weapons coz DW offhand for some reason goes to the top of my invent >.>