Back in the day one use to be able to swap trinkets in on the fly...and use of dmg trinkets use to stack. o.O

I havent tested this in arena, but I imagine it will still work. Arena doesnt allow one to change gear after the fight changes and this may also lock down relics.

I think this is wiki - worthy and I am surprised I haven't read about it anywhere else. I actually found this on arenajunkies.com.

Macro Form
/equip Name of Relic (Beneficial to the casting Spell)
/cast Spell

Example
Macro 1
/equip Totem of the Void
/cast Lightning Bolt

Macro 2
/equip Vengeful gladiators totem of the third wind
/cast Lesser Healing Wave

Macro 3
/equip Vengeful gladiators totem of Survival
/cast Earth Shock

This allows one to switch in the appropiate relic DURING combat and recieve the benefit to that spell! I think it PWNS face. Please /feedback