i recently bought the on-use PvP Trinket with SP and don't really know what to macro it into.
It was really easy for my paladin but i use my priest cooldowns differently in arena...
Power Infusion: Mainly used for Mana Burn in 2s, SP does not increase the mana burned so no point there.
Inner Focus: 45 sec cooldown that i use whenever its off cooldown and nobody can interrupt me, so no point there either IMO.
I was thinking maybe Shadow Fiend but the SF Cooldown is 5 mins and i could easily forget to use the trinket...
Or should i just keybind it and use it whenever i dont want to use a cooldown but heal for more?
I would go for the battlemasters spirit trinket but i get targeted alot and the extra resil is kinda necessary vs double dps in 2s (i know 2s unbalanced blabla)
I dont really have that much trouble with mana anyways, because i play with a moonkin and have a little innervate from him.
Personally I'd spec for the 4minute cd on sfiend, so mana troubles are lessened even more.
As for the on-use SP trinket, I wouldn't recommend using it, as the proc SP trinket is better for overall performance, as the increased spellpower once per 2 minutes isn't typically going to provide the necessary burst to keep someone up, the increased total healing allows for better mana efficiency due to less necessary heals over the entire match.
Just dont macro it, use it when needed for whatever reason. It may be harder to learn and set up, but it is the right way to do it and you will profit from it at the end.